Deanna Troi
Deanna Troi was a female Betazoid–Human hybrid Starfleet officer. Under the command of Captain Jean-Luc Picard, she served as the counselor aboard the  and the . In 2379, Troi transferred to the  (; ). By 2399, she and her husband William T. Riker lived on the planet Nepenthe with their daughter, Kestra Troi-Riker. Their son, Thaddeus Troi-Riker, died of Mendaxic neurosclerosis soon after their arrival on Nepenthe. ()

As a half-Betazoid, Troi was capable of extra-sensory empathy, but was incapable of reading aliens with brain structures dissimilar to Humans and other Betazoids, such as the Breen and the Ferengi. Like most Betazoids, Troi had telepathic abilities. Due to her half-Human heritage, however, the range of her telepathic abilities was limited compared to full-blooded Betazoids, and she could usually only read the thoughts of other Betazoids, most notably her mother. Troi's empathic skills made her an important asset to the Enterprise-D and her abilities were often particularly useful when dealing with hostile races. Since she could usually determine, through use of her abilities, whether others were lying, she repeatedly proved herself invaluable in many suspenseful situations. (; )

Early life and career 

Deanna was born on , 2336, near Lake El'nar on Betazed. She was born to Betazoid Ambassador Lwaxana Troi and Human Starfleet officer Ian Andrew Troi. Deanna was actually the second of their two children, the first being Kestra Troi, born in 2330. However, Kestra drowned when Deanna was an infant. Stricken with grief and regret, Lwaxana removed all evidence of Kestra's existence from her own life and even repressed all memories of Kestra. She also made her husband swear never to mention Kestra again. Because of this, Deanna did not learn of her sister until 2370, when Lwaxana's memories resurfaced. ()

As required by Betazoid custom, Deanna was genetically bonded with a Human male named Wyatt Miller at a young age. Wyatt was the son of Steven and Victoria Miller, close friends of Deanna's parents. Due to their genetic bonding, Deanna was scheduled to marry Wyatt in adulthood. ()

According to her mother, Deanna had a talent for languages as a child. () During her adult life, Deanna also recalled having visited  as a little girl, although she was not absolutely sure, as she always got "those museum ships" mixed up. ()

As a child living on Betazed, Deanna learned aspects of Human culture from her Human father, Ian. One such aspect was a fondness for stories set during Earth's Ancient West, which he often read to her. () To fall asleep, she would ask him to sing the American song "Down in the Valley"; while this was her favorite, it was his singing that made her feel safe. () As she was half-Human and half-Betazoid, she never felt trapped between the two worlds to which she belonged, instead choosing to embrace the richness of her dual heritage. () She also heard stories from her maternal grandfather, who told them telepathically; something of a traditionalist, he rarely spoke, saying speech was for "offworlders and people who didn't know any better." ()

Deanna's father died in 2343, when Deanna was only seven years old. Even so, she remembered him fondly, and when she became pregnant by an alien energy being in 2365, she named the child after her father. ()

In grammar school, Deanna had to memorize Jonathan Archer's speech at the Federation Founding Ceremony. () Deanna began studying psychology at the University of Betazed sometime in the 2350s. During her time there, one of her patients was Tam Elbrun, a Betazoid male who had been suffering from mental instability due to his lack of the Betazoid's natural ability to "tune out" the thoughts of others. ()

Deanna Troi entered Starfleet Academy in 2355. She graduated in 2359, majoring in psychology. () On her homeworld of Betazed, she met William T. Riker, a Starfleet lieutenant who was stationed on the planet. The two began a relationship sometime between 2357 and 2361, and the relationship lasted several years. After Riker was assigned to the , the two planned to spend their holidays together on Risa in 2361. However, Will had to cancel their plans after he was quickly promoted to lieutenant commander – deciding to make his career his top priority, Will stopped pursuing Deanna, and the couple eventually lost contact with each other. () By 2364, Troi held the rank of lieutenant commander. That year, she was assigned as ship's counselor aboard the USS Enterprise-D. ()

Aboard the USS Enterprise-D

2364-2365 

Troi proved herself to be an important asset to the crew of the Enterprise-D during the ship's first mission to Farpoint Station in 2364. Her ability to sense feelings and emotions yielded vital clues which allowed the crew to determine that the station was actually a shapeshifting space vessel lifeform being forced into servitude by the Bandi. By rescuing the creature and reuniting it with its mate, Troi and her shipmates managed to pass a test of Humanity's intentions imposed on them by Q. ()

Soon after, Troi was affected by polywater intoxication that caused her and the majority of the Enterprises crew to act out of character, but she was quickly taken to sickbay and provided with medical treatment. () Her empathic abilities were also useful a short time later, when she assisted in uncovering the intentions of Ligonian leader Lutan after he kidnapped security chief Natasha Yar. ()

Later that year, the Enterprise traveled to Haven, a legendarily beautiful planet near Beta Cassius. The planet was also the location of Wyatt Miller, who was scheduled to marry Troi as a result of their genetic bonding. Having expected that the marriage would not take place due to the years-long distance from her homeworld that serving aboard the Enterprise would cause, Deanna initially did not inform her crewmates of her obligation. Nevertheless, she agreed to honor her vows taken years earlier, even though she had since become doubtful of them and would need to leave the ship with her new husband once they had been married. While Deanna's mother, Lwaxana, and both Wyatt Miller's parents were aboard the Enterprise, a social gathering known as a pre-joining announcement was held to celebrate the forthcoming wedding. The marriage itself was permanently canceled, however, when Wyatt, a doctor by profession, chose to join his fantasy lover (a real woman he had had frequent dreams about) aboard an infected Tarellian vessel. ()

When a planet in the Delphi Ardu system drained the Enterprise of its power, Troi and the majority of the ship's crew suffered from exposure to extreme cold and were forced to endure almost deadly oxygen deprivation. ()

Upon first contact with the Ferengi species in 2364, Troi reported that she could discern neither thoughts nor emotions from them, giving her the initial impression that they could shield those from others. She later mentioned, however, that she could sense one of the Ferengi was hiding something. ()

Troi was unable to detect any feelings from the Traveler when he was encountered by the Enterprises crew in the same year. () However, she was later instrumental in discovering that an alien force had been invading the minds of crewmembers aboard the Enterprise and was influencing Captain Picard, who later temporarily blinded Troi while he was under the alien's influence. After Picard beamed himself and the alien into space, the crew believed that he could not be recovered, but Troi sensed that the captain had separated from the alien influence. Thanks to her advice, Picard was ultimately returned safely to the ship. ()

While searching for survivors from the doomed Federation freighter Odin, the Enterprise journeyed to the planet Angel I, becoming the first Federation vessel to visit the planet in sixty-two years. As Angel I was home to a female-dominated society, Troi, who commented early in the visit that a description of the planet made her suspect the location would be very much like her own homeworld, gratefully accepted the offer to make initial contact with Angels I's inhabitants and managed to arrange a meeting with a reticent head of the planet's government. ()

Later that year, Troi was returning from a conference when her shuttle suffered a sudden instrument malfunction and subsequently crash landed on Vagra II. There, a lonely but sadistic entity that referred to itself as Armus held Troi prisoner by surrounding her shuttle with a force field and prevented her crewmates from rescuing her, even going so far as to kill Lieutenant Yar. Troi and her shuttle pilot, Lieutenant Ben Prieto, were eventually rescued after Wesley Crusher and Worf discovered that the field weakened when Armus was provoked, due in part to Troi's intelligence regarding Armus' emotional state and psychology. ()

Near the end of her first year aboard the Enterprise, Troi was looking forward to a moonlight swim on the ship's oceanic destination of Pacifica, an experience she believed could not adequately be replicated by the ship's holodeck. She did not get the opportunity to enjoy her swim, however, as the Enterprise was diverted to Dytallix B and then to Earth. () Deanna later helped Clare Raymond, a recently revived Human from the late 20th century, learn about her descendants and locate distant relation Thomas Raymond. ()

In early 2365, Troi became pregnant by an alien who wished to experience Human feelings and relationships. He grew at an accelerated rate and within hours was an eight-year-old boy. At the same time, a plasmic plague struck the ship and threatened to kill everyone within hours. The alien realized that he was the source of the plague and sacrificed his Human life to save the ship, reverting to his alien form and then leaving the craft. Troi experienced both the joy of childbirth and the heartbreak of losing a child. ()

Later that year, when Ira Graves downloaded his memories into Data, Troi discovered that the changes in Data's personality were actually Graves. ()

2366-2367 

The next year, Troi fell for a delegate, Devinoni Ral, at a conference for the rights to a wormhole. Troi and Ral had an instant attraction to each other. She learned that he was part Betazoid and had been using his mental powers to influence the negotiations. When the Ferengi threatened to blow up the wormhole, stating that there was a secret deal between the Federation and the Barzan, Troi suspected that this was staged by Ral to acquire the rights to the wormhole. The Barzan gave the rights to Ral, but it was soon discovered that the wormhole was unstable and worthless. Ral quickly left and bade goodbye to Troi. ()

Troi thereafter met her former patient Tam Elbrun again, when he was being transported by the Enterprise on an ultimately successful mission in which Elbrun made first contact with and subsequently remained with an alien lifeform that looked like an organic spaceship and was called "Tin Man". ()

Troi became the object of affection for a new crewmember named Reginald Barclay. He was too shy to approach her, so he created a holoprogram to interact with her. Troi counseled him, and he eventually ended the program. ()

While attending a trade conference on Betazed, Deanna, along with Lwaxana and Riker, were captured by the Ferengi, who wanted to use Lwaxana's telepathic abilities to give them an advantage in negotiations. They used mind probes on Deanna and Lwaxana, but Riker was able to send a message to the Enterprise, communicating the location of the Ferengi ship, and they were then rescued. ()

Troi temporarily lost her powers when she came in contact with two-dimensional lifeforms that had caught the Enterprise in their magnetic force. They were heading for a cosmic string which would destroy the Enterprise. Picard asked her to use her Human abilities to try to determine the aliens' intentions – as he pointed out, her degrees in psychology were not tied to her powers and she was still the most qualified person on the ship for the task. Troi determined that the cosmic string was their home; the Enterprise was able to break free, and after the aliens left, her powers returned. ()

While investigating the , which had become stranded in space, the Enterprise found one crewmember alive, a Betazoid science adviser. The rest of the crew had killed each other. The Enterprise crew discovered that the ship was caught in Tyken's Rift, which sapped all the energy from the ship. Additionally, the crew of the Brattain had succumbed to madness through sleep deprivation from an unknown cause. The same thing was happening to the Enterprise. The crew was on the verge of madness, and only Data and Troi were unaffected, as Data did not require sleep and Troi's partially Betazoid physiology processed dreams at a different frequency. Data believed that an explosion would get them out of the rift, but the plan failed. Troi had experienced a single, recurring nightmare, but determined that it was an act of communication from other beings stuck on the other side of the rift. This communication had caused the dream states of the rest of the crew to become disrupted. In a dream state, she relayed a plan of cooperation that would release each ship. Her plan worked. ()

2368-2369 
Troi took command of the Enterprise after it was hit by a quantum filament that caused major damage and trapped the officers in various parts of the ship. She decided not to separate the bridge and engineering, and to divert power to engineering, a decision that ended up saving the ship. ()

Troi counseled Worf and Alexander Rozhenko, who had boarded the ship to stay with his father. Her efforts helped stabilize their relationship. Whereas Worf was about to send his son to a Klingon school, Troi observed that the boy was difficult because of the death of his mother, leaving him with a feeling of abandonment, and that sending him away would only make the boy worse. ()

During a visit by telepathic aliens, Troi was attacked and lapsed into a coma. On waking, she believed she had been attacked by Riker. She ultimately discovered, though, that one of the aliens, who had participated in the attack, had been using his telepathic powers to make her think her attacker had been someone else than he himself. ()

While helping to save a closed society of genetically-engineered Earth colonists, Troi became romantically involved with their leader, Aaron Conor. After the colony was saved, the romance ended as she returned to the ship and he declined to leave his colony. ()

Troi's body was taken over by an alien spirit after the Enterprise investigated the disappearance of the , an event that had occurred almost two hundred years previously. Troi, along with O'Brien and Data, was possessed and hijacked the Enterprise, taking hostages in the process. The Troi alien stated that he was Bryce Shumar, captain of the Essex, and that he and his crew's spirits had been caught up in the magnetic field of the moon. He asked that their bones, which were on the planet, be returned to Earth, so that their spirits could rest. Picard did not believe "Troi", and found out that she wished to return to the planet to get the other alien spirits, so they could take over the crew's bodies. The moon was actually a penal colony, and the spirits were really criminals. After Picard threatened to destroy the Enterprise and their existences, the spirits decided to stay alive on their moon. ()

After Lwaxana boarded the Enterprise and announced that she planned to marry (again), Troi's attempts to counsel Alexander, Worf's son, about meeting his responsibilities were disrupted by her mother. Deanna also became upset that her mother was not going to follow the traditional Betazed marriage rituals. In reality, Lwaxana was suffering a mid-life crisis, and in the end, she terminated her relationship with her suitor. ()

In 2369, Troi met Ves Alkar, a Federation mediator who routinely transferred, telepathically, his dark thoughts and emotions to other hosts, so that his mind was clear and able to mediate conflicts more effectively. After Alkar's previous receptacle expired, Troi was tricked by him into performing a "funeral meditation", which established a link – deliberate on Alkar's part – between them. The effect of this transfer caused Troi to act aggressively and, due to the fact she was a non-Lumerian, to experience rapid aging faster than his previous victims. Before Alkar left for a conference, Troi attempted to use a knife but Picard stopped her. After that, Troi was taken to sickbay by Riker, who was the first to know something was wrong due to knowing her better then anyone, and two security guards so Dr. Crusher can help her. When Alkar refuses to release Troi, Dr. Crusher induced death-like symptoms, to trick Alkar into severing the link by trying to take another female Lumerian as his receptacle, at which point Troi was revived by Crusher and the Enterprise crew thwarted Alkar. ()

Troi later participated in an Old West holodeck program with Worf and Alexander. It became too real when a malfunction released the safety protocols as a result of Data interfacing with the Enterprises computers, causing the characters to take on the android's appearance and abilities. Troi helped Worf rescue Alexander and put the outlaws in jail. ()

Later in 2369, Troi was kidnapped and surgically altered by the Romulan underground movement. She was forced to assume the role of Major , an operative for the Tal Shiar, aboard the . While there, Troi befriended Sub-Commander N'Vek, who helped her to adopt her role and also revealed the true nature of her mission – to help Vice-Proconsul M'ret and two of his aides defect to the Federation. Troi discovered that she wielded much  over the crew of the Khazara, as many people were frightened of the Tal Shiar. However, she had a conflicted relationship with the Khazaras commanding officer, Commander Toreth. When Troi's mission took a turn for the worse and a fight with the Enterprise seemed imminent, Deanna seized command of the Khazara. She managed to successfully complete her mission by concealing a transporter beam inside a low-level disruptor blast. N'Vek was killed by the Khazaras helmsman after Toreth retook command, and the Enterprise barely managed to beam Deanna back on board before the Khazara fled under cloak. ()

Troi, along with Picard, Data, and Geordi La Forge, returned from a conference to find the Enterprise and a Romulan ship suspended in time, a condition caused by aliens who were using the warp core as an incubation for their young. While helping to investigate the situation, Troi demonstrated her knowledge of Romulan engineering principles, acquired during her time aboard the Khazara. She and her companions drove out the aliens, after which the timeline was restored. ()

At the end of the year, Troi, together with Picard and La Forge, was captured and imprisoned by Lore, who planned to lead a group of individualized Borg drones to destroy the Federation and had brainwashed Data into helping him. Troi and her inmates stole a transceiver that they used to restore Data's ethics. The prisoners were finally rescued by Hugh, Data, and the Enterprise. ()

2370-2371 

When the Enterprise took part in a cultural exchange in early 2370, Troi served as the liaison for Loquel. She was frustrated by his behavior to the point she felt as though she was going crazy, as all he wanted to do was indulge himself and party. Eventually, she discovered his assignment was to experience pleasure. ()

Supervised by Riker without any favoritism towards her, Troi tried to pass the Bridge Officer's Test in 2370. She attempted the engineering qualification several times without much luck, after which Riker told her the tests were canceled. However, he also gave her a hint which let her know that the test was really about her ability to send a crew member to his death. Troi went on to successfully pass the test. She was then promoted to the rank of commander and began to include bridge command as part of her duty shifts. With this development, Troi acquired Starfleet status as a line officer, in addition to her previous status as a staff officer. ()

Troi helped save her mother's life when Lwaxana was suffering a severe mental breakdown due to a long-repressed memory. With the help of a telepathic alien, Deanna managed to enter into her mother's mind and find the source of the mental trauma. She found out she had once had an older sister who had died in a drowning accident that Lwaxana blamed herself for. Deanna was able to help Lwaxana accept the death and convince her that she was not to blame. ()

After a crewmember, Daniel Kwan, committed suicide on board the Enterprise, Troi was asked to investigate, since the crewman had had empathic abilities and Troi might be able to find out why he had killed himself. After examining Kwan's station, Troi became insanely jealous of Worf; when she found him in the arms of another female crewmate, Troi killed Worf and attempted suicide. She was preparing to jump to her death when Worf, who was actually still alive, saved her. It turned out that everything Troi had experienced had been in her mind. When the Enterprise-D had been under construction, one of the crew, an empath, had committed murder and suicide, leaving an empathic message that had been picked up by Kwan, leading to his death. Troi had picked up the same message, but had been more fortunate. ()

In 2371, Troi piloted the Enterprise-D on the orders of Commander Riker during the Battle of Veridian III. The warp core breach that destroyed the ship's secondary hull knocked the primary hull out of orbit, and she was forced to pilot it to a crash-landing on the planet. Despite her inexperience as a pilot and having to land in rugged terrain, she succeeded in bringing the ship down, saving the crew with minimal casualties. She was the last person to pilot the Enterprise-D, as the saucer section could not be salvaged. ()

Aboard the USS Enterprise-E 
In 2372, Troi transferred to the  USS Enterprise-E, with most of the senior staff of the Enterprise-D. () She continued the occasional role of bridge command as part of her duty shifts, while posted to the Enterprise-E. ()

In 2373, Troi and her crewmates disobeyed Starfleet orders by taking part in the Battle of Sector 001. The Enterprise was instrumental in the destruction of an invading Borg cube but pursued a remaining Borg sphere back in time to 2063, subsequently destroying the Borg craft before it could prevent the historic first flight of Zefram Cochrane's Phoenix warp ship.

After the Borg attack, two teams of officers beamed to the surface of Earth, with Troi serving as a member of the second team. She searched for Zefram Cochrane on the planet and accepted a civilian's offer of a drink in return for information. After three shots of tequila, Troi, having become extremely drunk, discovered that the civilian was actually Zefram Cochrane himself. After she and the inventor were found in a bar by Riker, Troi continued to share a drink of extremely strong tequila with Cochrane, who she officially reported was "nuts", before losing consciousness due to her large consumption of alcohol.

After she came to, Troi helped to convince Cochrane of the importance of his first warp flight, which he was considering canceling following the Borg attack. Troi later supervised the launch of the Phoenix from Earth, Cochrane blasting the song "Magic Carpet Ride" in her ear, a few seconds before launch. By overseeing the launch, she assisted in preserving what followed the historic flight: First Contact between Humans and Vulcans. ()

Two years later, in 2375, Troi helped Captain Picard prepare to host a reception for a visiting delegation of Evora representatives – after having read a Starfleet report on their species – and later attended the ceremony with Picard, Riker, and Dr. Crusher. Later, Troi alone downloaded all Starfleet records on the Son'a and studied them with Riker. She was also in command of the bridge just before the Enterprise-E arrived at the Briar Patch. Upon encountering members of the Ba'ku – whom the Son'a had been observing until recently – Troi used her empathic abilities to sense that several Ba'ku children present had incredible mental discipline and clarity of perception.

After it was learned that the Son'a were attempting to discreetly relocate the Ba'ku from their planet, Troi helped to evacuate the Ba'ku from their village to the safety of a mountain range. Around this time, she noticed that her breasts had started to firm up, a result of the age-decelarating properties of metaphasic radiation in the Ba'ku planet's rings. She also helped eliminate Son'a drones, but after Picard and a Ba'ku woman became trapped following a cave-in, her plan to cut away rock using her phaser was discarded, as it was thought to be too dangerous. Once the two imprisoned humanoids were released, Troi stayed with the refugees as most of the other senior officers left to successfully prevent the Son'a from relocating the Ba'ku, who were actually their own distant relations. ()

Project Pathfinder 
In 2376, Deanna Troi visited Lieutenant Reginald Barclay while she was enjoying shore leave on Earth. Barclay, an old friend of hers from the Enterprise-D and -E, told her about his role in the Pathfinder Project – a mission to determine a method of communicating with the , stranded in the distant Delta Quadrant. Barclay, using a holographic simulation of the starship and its crew, had devised a plan to contact Voyager, but had become obsessed with the starship. Troi feared that he was suffering from a relapse of holo-addiction, a condition he had previously recovered from with her assistance. Although Troi was scheduled to leave Earth aboard the Enterprise the next morning, she decided to ask Captain Picard for a temporary leave of absence, so that she could spend some time with Barclay. Later that night, Barclay left his apartment and headed to Starfleet Command, where he finally managed to establish communication with Voyager. Deanna later shared a drink with Barclay to celebrate his success. ()

Troi was serving aboard the Enterprise when Barclay contacted her from Jupiter Station. His friend and the inventor of the Emergency Medical Hologram, Doctor Lewis Zimmerman, was terminally ill on Jupiter Station and was only expected to live a few more months. The officers aboard Voyager had managed to send a member of their crew, a Mark I EMH named simply The Doctor, to Jupiter Station, but Dr. Zimmerman was refusing to be treated by The Doctor, whom he saw as inferior to the later Mark III and Mark IV EMHs.

Barclay suspected that Troi might be able to persuade Zimmerman to allow The Doctor to cure him before he died. Although the Enterprise was in the middle of a mission almost seven light-years away, Troi agreed that the plan sounded like an interesting challenge and requested leave from Captain Picard. A week later, she arrived at Jupiter Station but was unable to mediate an agreement between the two doctors. She and Barclay eventually came up with an alternative strategy: create a malfunction in The Doctor which Zimmerman would have to repair, thereby bringing them closer. It worked according to plan. ()

In 2377, Troi was sunbathing on a beach when Barclay crept up on her. He told her that he had created an advanced interactive hologram in his own image with the express purpose of sending it to Voyager, but the program had gone missing on its way to the starship. Troi helped Barclay and his supervisors at the Pathfinder Project determine that the crew of a Ferengi casino ship had stolen the hologram. Troi and Barclay discovered that the Ferengi had reprogrammed the hologram and sent it to Voyager in an attempt to acquire Borg nanoprobes from Seven of Nine. After the casino ship opened a geodesic fold – a gateway to the Delta Quadrant – Troi suggested sending a warning message to Voyager through the geodesic fold, but Barclay told her that subspace transmissions could not pass through the anomaly.

Instead, Barclay contacted the casino ship from the Voyager simulation at Starfleet Command while Troi stood next to him and watched from outside the Ferengi's view. Pretending to be his hologram, Barclay told the Ferengi that Captain Janeway had discovered their plan and was furiously preparing to attack with powerful weaponry. The Ferengi believed the trick and closed the geodesic fold. Shortly before Deanna left San Francisco, Barclay was working on programming another version of his hologram with security protocols so it couldn't be stolen again. She convinced him to get out of the office and start experiencing life again, namely by going out on a double-date with herself and Riker, and Riker's friend, a teacher named Maril they wanted to introduce to him. ()

Marriage and transfer 

Will Riker and Deanna married in 2379, shortly before their transfer to the . Their wedding party in Alaska included Captain Picard as best man, Dr. Crusher as bridesmaid, and Data, La Forge, Worf, and Wesley Crusher as groomsmen. Guinan was also present. Another ceremony, a traditional Betazoid wedding, was planned on Betazed shortly following. However, that ceremony was delayed when the Enterprise was diverted to Romulus. ()

In 2379, Troi made her final voyage aboard the Enterprise as the ship journeyed to Romulan space on a diplomatic mission in which she and her crewmates met new Reman Praetor Shinzon. Aboard the Enterprise, Troi was telepathically violated by Shinzon, who seemed obsessed by her. She used their residual link to her advantage, however, during the Battle in the Bassen Rift; after the Enterprise was nearly disabled, Troi took the helm and, under Captain Picard's orders, crashed the ship into Shinzon's Reman warbird, the Scimitar, further disabling that craft. Troi was later saddened to learn that the fatalities of the battle had included not only Shinzon but also Data. She subsequently joined the USS Titan under Riker's command, and was due to return to Romulus on another diplomatic mission. ()

Aboard the USS Titan 

In 2380, Troi was on the Titan, when that ship saved the  when it was attacked by the Pakleds. ()

About a year later, Troi would give birth to her and Riker's first child, Thaddeus Troi-Riker. ()

Life after Starfleet 
Troi and Riker, along with their two children, Thaddeus Troi-Riker and Kestra Troi-Riker, settled on the planet Nepenthe in an effort to mitigate Thaddeus' Mendaxic neurosclerosis. Unfortunately, the disease proved fatal, and Thaddeus died. He would have survived had the Federation not imposed a ban on synthetic lifeforms after the 2385 attack on Mars. ()

Retired Admiral Jean-Luc Picard arrived on Nepenthe in 2399 with Soji Asha, whom Troi could not sense any emotion from, and Riker immediately recognized as being an android descended from Data. As Picard had expected, Riker and Troi both offered to help him without hesitation, opening their home to him and Soji for as long as they needed. ()

Personal interests

Exercise 
Deanna enjoyed swimming, but didn't think swimming on the holodeck was an adequate substitute for swimming in a real ocean. () She often used exercise programs on the holodeck, though, when she needed to take her mind off frustrations. ()

Troi and Beverly Crusher often exercised together. () With Crusher, Troi also took mok'bara classes. ()

Chocolate 
Deanna once said that she had never met a form of chocolate that she did not like. () Data mentioned to Q that, when Counselor Troi was in a bad mood, she often ordered a food containing chocolate. () Dr. Crusher once described Counselor Troi as loving chocolate. ()

Poker 
Aboard the Enterprise-D, Troi enjoyed playing poker with her crewmates. She was not known to bluff, according to Worf, but was quick to point out that perhaps she was good enough that he simply never caught her. ()

Music 
Troi once idly played a melody on a piano on Moab IV. ()

Personal relationships

Friendships

Beverly Crusher 
Deanna Troi and Beverly Crusher became very good friends. They often worked out together and took mok'bara classes, taught by Worf. ()

Deanna and Beverly often advised each other on romantic relationships. At one point, Deanna worried that her romance with Devinoni Ral was proceeding too fast, but Beverly assured her that perhaps she did not need to be rational regarding a whirlwind romance. ()

While Crusher was using the salon aboard the Enterprise-D, Troi arrived there and was surprised to find Beverly using the salon at the same time, as Crusher rarely visited the salon. Recognizing romantic feelings Crusher had about Trill Ambassador Odan, Troi happily admitted to Beverly this detection of romance, even though Beverly and her paramour were trying to keep their relationship a secret. However, Troi also sensed the dual nature of the ambassador, and warned Beverly to be cautious. Later, when the Odan host was implanted in Will Riker's body, Deanna counseled Beverly, in a discussion they had in Ten Forward, on the mixed feelings Crusher then felt towards Odan and Riker. Although Beverly wished she had never met Odan, Deanna advised Beverly not to wish such a thing and mused that to love was impossible without risking pain. Troi encouraged Beverly to accept Odan's love if she still felt it while he was in Riker's body. ()

When time-traveler Berlinghoff Rasmussen came aboard the ship, Troi didn't trust him and told Crusher about her feelings of suspicion. ()

After the Enterprise rescued transporter duplicate Thomas Riker from a research station on Nervala IV in 2369, the possibility of Troi entering a romantic relationship with him came up, since Tom Riker – as a duplicate of Will Riker – had memories of having had a relationship with Deanna and was interested in pursuing a romance with her. Troi and Crusher chatted about a date with Tom during a workout, where Crusher mischievously pointed out that Troi should not be afraid to try a relationship with the duplicate Riker. When Tom Riker entered the gym and Beverly then decided to leave the two alone, Troi was initially shocked by Crusher's departure, but it led to Deanna becoming intimate with Tom. ()

Deanna accompanied Beverly to Felisa Howard's funeral in 2370 and back to Felisa's home following the services. She counseled Beverly about erotic dreams Crusher had experienced after reading her grandmother's journals, dreams which were due to the influence of Ronin. After Beverly met Ronin on Caldos, Deanna reminded her that her feelings of romance might simply be due to shared trauma, but Beverly brushed off her concern. ()

Reginald Barclay 

Troi's relationship with Reginald Barclay did not start off very well. Because he was intimidated not only by Troi's beauty but by her status as ship's counselor, he even went as far as to meet with a holographic version of her rather than with the real Troi. In Barclay's holoprogram of The Three Musketeers with the senior staff serving the primary roles, Troi told Riker and La Forge that there was nothing wrong with a healthy fantasy life, until she found her likeness was the Goddess of Empathy. After this incident, she began a real-world counseling relationship with Barclay, including helping him through his bout of transporter phobia. () This counseling relationship eventually turned into friendship, and Barclay called upon her to help him when he was assigned to the Pathfinder Project. ()
See Project Pathfinder section.

Natasha Yar 
Troi was tearfully angry when Lieutenant Yar was frozen by Q during a trial ceremony at which he acted as judge, and she furiously shouted, "You barbarian!" at Q. ()

While Yar was infected with polywater intoxication later that year, Troi was startled to find Yar in her quarters, Yar having sought Troi for advice regarding her hair and clothes. Even though the lieutenant seemed playfully content, Troi sensed that she was actually very uncertain and was fighting something. Concerned for her crewmate and friend, Deanna asked Yar what was wrong and, after the lieutenant left without answering the question, immediately reported her strange behavior to Captain Picard. Unknown to Troi at the time, however, she herself had contracted the polywater intoxication from Yar during their brief encounter. ()

After Yar was kidnapped by Ligonian leader Lutan, Troi helped uncover the intentions of her friend's captor, remarking at one point that she believed Yar was physically very attractive. After Lutan announced his decision to make Yar his First One, Deanna tricked the lieutenant into admitting, in the presence of Captain Picard, that she had felt good when Lutan had said he wanted her. Troi's deceit shocked Yar, as she regarded Deanna as a friend, but the counselor explained that she had used deception only so that Yar would answer honestly how she felt about Lutan. Troi later argued in favor of Yar's partaking in a fight to the death against a challenger to her entitlement, advising Picard that the lieutenant would easily be able to beat her opponent – Lutan's current First One, Yareena. ()

Family

Lwaxana Troi 

Deanna had a tense relationship with her mother and was often visibly irritated when Lwaxana showed up on the  unannounced. Also, Deanna was often not as concerned about her own love life as her mother was. Going over Lwaxana's diary entries from 2365 to that present year of 2370, Deanna wryly noted that the only "bad" thing she could find were references that she was still unmarried at the time. ()

Ian Andrew Troi 
Deanna was devasted by her father's death once she fully understood that he wasn't coming home again after he suddenly died in 2343, when Deanna was around seven years old. She remembered him fondly, years later. When she became pregnant by an alien energy being, Deanna named the resulting child after her father. ()

Kestra Troi 
Deanna Troi was only a few months old at the time her older sister, Kestra Troi, died during a family picnic they went on with their parents. Since Lwaxana buried the memory instead of dealing with the loss, Deanna did not know anything of Kestra Troi until 2370. She would go on to name her own daughter Kestra years later in her sister's memory. (); )

Alexander Rozhenko 
When Worf's son Alexander came to live with him on the Enterprise, Troi played a significant role in helping Alexander define and develop a relationship with his father, as well as assisting Worf's bond with his son. When Worf was severely injured in 2368, Deanna was requested, by Worf, to look after Alexander if Worf died; as Worf saw it, she was the best person to care for his son. () Deanna's affection for Alexander was reciprocated, as Alexander came to trust Troi and developed a great affection for her, and an even greater affection for her mother, Lwaxana. () In late 2370, Deanna gladly accepted a request from Worf that she formally become Alexander's Soh-chIm, an honorary role equivalent to that of a godmother. ()

Romance

William T. Riker 

Deanna had an extremely close relationship with Will Riker, occasionally referring to him as imzadi, a Betazoid word for "beloved". Before they served together on the Enterprise-D, Troi taught Riker how to read her thoughts when she telepathically projected them. They learned each other's abilities but couldn't say "goodbye" when they parted.

After Troi was assigned to the Enterprise-D in 2364, she was reunited with Riker. Although they informed Captain Picard that they already knew each other, neither Riker nor Troi initially revealed the intimate nature of their former relationship. Troi seemed fairly eager to be alone with Riker, and while at Deneb IV's mysterious Farpoint Station, she suggested that they explore a network of passages below the station together, an idea that Riker refused. Before he later endangered his own life to investigate why a space vessel lifeform believed to be a ship was attacking Deneb IV, Troi expressed, in an outburst of emotion, her extreme fear that Riker could be hurt. She soon managed to resume her former sense of calm, however, and returned to the Enterprise, as Riker had ordered. ()

During the Enterprises subsequent missions, Troi referred to Riker as "Bill" on at least two occasions. ()

While under the influence of polywater intoxication, Troi was drawn to Riker, and in an attempt to seduce her former lover, she sensuously embraced him in main engineering. When he picked her up in his arms and began carrying her to sickbay, she asked if he wouldn't rather be alone with her in his mind than ensuring she was hospitalized. Riker, however, did not surrender to her seduction and succeeded in taking her to sickbay. ()

Troi and Riker were later asked by Captain Picard to exhibit use of the Enterprises holodecks to a party of Ligonian representatives, while the group of Ligonians were negotiating with the ship's crew upon visiting the vessel. When Ligonian leader Lutan instead requested that Lieutenant Yar demonstrate defense training in one of the holodecks, Picard's request went unanswered and Troi lost the opportunity to work solely with Riker. ()

Troi's life, as well as the lives of virtually the entire crew of the Enterprise, was later saved by Riker when he managed to persuade Portal 63 of the long-extinct Tkon Empire to release the starship from his control, as the Portal had trapped the Enterprise in an energy field that was draining the ship's power and forcing its crew, including Troi, to endure extreme cold and almost deadly oxygen deprivation. ()

During the Enterprise-E's mission to Ba'ku in 2375, Deanna and Will were affected by the metaphasic radiation of the planet's rings, which eventually led to their reviving their relationship. () Deanna and Will Riker married four years later. () 

They settled on the planet Nepenthe with their two children, Thaddeus Troi-Riker and Kestra Troi-Riker. Thaddeus died of Mendaxic neurosclerosis, which could have been cured with a positronic matrix had the Federation not imposed a ban on synthetic lifeforms after the 2385 Attack on Mars. ()

Worf 

Although Worf was distrustful and uneasy around telepaths, Troi became a trusted exception. There was some early antagonism between them, especially when he insisted that her unexpected pregnancy (with Ian) had to be aborted for the safety of the ship. But she later helped him adjust to his new role as a father to his son, Alexander, at which time Worf grew to trust and respect Troi. ()

After an encounter with alternate realities showed him a life with Troi as his wife, Worf's eyes were opened to a new possibility, and he began to pursue her. Though surprised, Troi welcomed the advances, and the two enjoyed a romantic relationship through 2370. Deanna wasn't thrilled by Worf's concern about Riker's interest in the matter, but the triangle's tension was eased by the advice of Captain Picard. ()

By the next year, the romance seemed to have dissolved amicably. Worf transferred to Deep Space 9 and began a romantic relationship with Jadzia Dax, with the two later marrying. Troi and Riker resumed their relationship around the time Worf was grieving Jadzia's death. Worf's only visible unease at their wedding in 2379 was the result of imbibing too much Romulan ale and discomfort at the prospect of appearing naked at their Betazed marriage ceremony. (; ; ; )

Alternate realities and timelines 
In an alternate timeline briefly created in 2366, Deanna Troi was not serving as a senior officer aboard the Enterprise-D when the ship encountered its predecessor, the  starship . There was no one shown to be serving as ship's counselor in her place, suggesting that the position did not exist due to the constant state of war in that timeline. ()

In 2369, Q sent Captain Picard into an alternate timeline in which he was a mere lieutenant jg assigned to the Enterprise-D as an assistant astrophysics officer. Although Troi and the other senior officers were less familiar with Picard than they were in his own universe, she and Riker provided advice he sought from them regarding his career prospects. Deanna was eager to leave the meeting, believing that Ten Forward was not the best place to have their discussion, but shortly before leaving the room with Riker, she suggested to Picard that they meet later to resume their conversation. ()

In 2370, Lieutenant Worf encountered a quantum fissure that caused him to begin shifting between quantum realities. In at least one universe, Troi participated in a surprise celebration for Worf's birthday. Later, Troi spoke with Worf about his son, Alexander, and graciously accepted his offer to serve as his son's Soh-chIm, formalizing her motherly relationship with Alexander. In two other universes that Worf visited, Troi was married to him in an extremely loving relationship. In the first of those universes, Deanna's romantic affiliation with Worf had begun approximately three years earlier, after he had sought Riker's formal permission to court Troi, in the belief that to do otherwise would be dishonorable. In the latter of the two universes, Troi was the mother to two children that Worf fathered, and he was the Enterprises first officer. They had a son named Eric-Christopher, who was born in 2367, and a daughter named Shannara, who was born in 2368. However, Troi had no knowledge of Worf's son, Alexander. Although she believed that the Worf who was indigenous to her own universe might not return, Troi kissed Worf goodbye before the Klingon departed her ship in the , a Type 6 shuttlecraft. ()

In an unknown, alternate future timeframe, Troi died from unknown causes, and a funeral was held in her memory. Both Worf and Riker were extremely saddened by her demise, and each blamed the other for preventing a relationship with her, causing relations between the two men to become estranged for the next twenty years. ()

Holograms 

Deanna Troi has been holographically duplicated on a number of occasions.
In 2366, Reginald Barclay, while suffering from holo-addiction, created at least two holographic characters based on Troi in his holodeck fantasy worlds. One referred to itself as the Goddess of Empathy and wore a toga-like garment while displaying aggressively flirtatious and exhibitionist tendencies. ()

In 2367, a holographic version of Troi featured in a holographic illusion which Barash trapped Riker in and which was set in the year 2383. This illusory Troi had similarities and differences to the actual Troi, looking older but acting as if she could still sense the feelings of others. Having supposedly accepted a position at Starfleet Command offered to her by "Admiral" Picard, the fictional Troi held a commander's rank and served as Picard's aide, no longer assigned to the Enterprise-D. As the Federation was on the verge of signing a peace treaty with the Romulans, Troi accompanied Admiral Picard aboard the , a Romulan Warbird that also carried Ambassador , from Romulan space to the Enterprise. In a conversation with Riker, Troi spoke highly of "Min", a now-deceased woman who had married him and had replaced her as ship's counselor following her departure from the Enterprise. However, after Riker discovered that the woman Troi had referred to was apparently Minuet (a holographic fantasy character he had once created), Troi tried to prevent him from angrily demonstrating the errors of the illusion by encouraging him to become calm. The illusion ended shortly thereafter. ()

In 2369, a hologram of Troi was created by  as part of a holographic illusion to trick Captain Picard into releasing his control over the Enterprise-D. ()

Miscellaneous information 

Troi frequently wore casual attire while on duty, possibly due to her position as ship's counselor. (, et al.) However, while serving under Edward Jellico in 2369, she was ordered to wear a standard duty uniform, which she began doing at that time. She continued to use the uniform after Captain Picard resumed command. ()

Troi's quarters aboard the Enterprise-D were located at deck 9, room 0910. ()

Troi was able to beat Data in a game of three-dimensional chess, using "intuition." When faced with the Kriskov Gambit, instead of countering with the el-Mitra Exchange as is characteristic, Troi chose to leave her king vulnerable, devising a completely unanticipated response to a classic attack, and forcing checkmate in seven moves. ()

Among the holographic environments that Troi visited are sickbay and engineering aboard the  starship Voyager, and the bridge, captain's ready room and engineering aboard the  starship Enterprise. (; )

Despite being half Human and half extraterrestrial by Human standards, Troi was able to participate, without disguise, in away missions that involved traveling to periods of Earth's past before official First Contact took place with the Vulcans. This was because, externally, Betazoids were physically indistinguishable from Humans in every aspect but one: the irises of their eyes were completely black. Humans are known to have irises a very dark brown so as to be nearly black, so this wasn't a telling feature in any case. () (; )

Troi did not like riding horses because of their "own mind", as Betazoids become too involved in the thoughts and shifting passions of animals. ()

Lwaxana mentioned her daughter while talking to Constable Odo aboard Deep Space 9 in 2369 and remembered her experiences with DaiMon Tog. (; )

In 2380, Beckett Mariner mentioned Troi to Brad Boimler as a prominent Starfleet officer. ()

Chronology 

 2336: Born on Betazed to Ian Andrew Troi and Lwaxana Troi
 2336: Older sister, Kestra, drowns
 2343: Father, Ian Andrew Troi, dies
 2350s: Begins studying psychology at University of Betazed
 2359: Meets and begins relationship with Starfleet officer William T. Riker
 2359: Graduates from Starfleet Academy
 2361: Breaks off romantic relationship with Riker
 2364: As Starfleet officer with rank of lieutenant commander, assigned aboard  as ship's counselor
 2364: Prearranged marriage to Wyatt Miller is called off
 2365: Son, Ian Troi, is born and dies
 2370: Promoted to rank of commander after passing Bridge Officer's Test
 2371: Successfully pilots Enterprise-D's saucer section in safe crash landing on Veridian III, immediately following saucer separation after Battle of Veridian III
 2372: Assigned as ship's counselor aboard 
 2375: Rekindles romantic relationship with William T. Riker
 2379: Married to Riker in ceremonies held on Earth and later on Betazed
 2379: Transfers aboard  with Riker
 2381: Gives birth to son, Thaddeus Troi-Riker
 2399: Living on planet Nepenthe with Riker and their daughter, Kestra Troi-Riker. Thad died several years prior.

Appendices

Appearances 
Deanna Troi appears in 169 of the 178 episodes of Star Trek TNG. Thus only the 9 episodes she does not appear in are listed here for brevity. 

 All episodes except for:

:

Background information

Performers 
Deanna Troi was played by actress Marina Sirtis. The baby Deanna Troi in  was played by twins Candace and Nicole Villwock.

Concept origins 
The original concept for the character of Deanna Troi was partly inspired by Ilia, a likewise empathic character created for the abandoned series Star Trek: Phase II before ultimately appearing in . Similarly, Troi's relationship with Riker has its conceptual roots in Ilia's relationship with Willard Decker from Star Trek: The Motion Picture. (Star Trek: The Next Generation - The Continuing Mission, p. 23)

Originally, Deanna Troi was meant to be a very cerebral character. David Gerrold once recalled, "Bob Justman and I spoke about a person aboard ship who serves the function of an emotional healer. Not a chaplain, because we have moved beyond mere ritual, but someone who serves as a 'master.' His/her job is to support those aboard the ship in the job of being the best they can be. That would eventually become Deanna Troi." (The Fifty-Year Mission: The Next 25 Years, p. 100) Stated Marina Sirtis, "Gene [Roddenberry] had the idea of this character because he felt that in the 24th century mental health should be as important as physical health." (SFX: The A-Z of Star Trek, p. 82) Sirtis also remarked, "Troi was not supposed to be the chick on the show. Gene [Roddenberry] said she was intended to be the brain on the show." (The Fifty-Year Mission: The Next 25 Years, p. 101) Denise Crosby added, "The original description of Troi was this cool, Icelandic blonde." 

At one point, Marina Sirtis likened the original concept of Troi to Spock, commenting, "She was supposed to have equal the intelligence of Spock." (The Fifty-Year Mission: The Next 25 Years, p. 101) Denise Crosby agreed that the original notion of Troi was "almost Spock-like."  However, the addition of Troi to the mix of TNG's main characters was actually an attempt to differentiate TNG from . (The Fifty-Year Mission: The Next 25 Years, p. 99) Furthermore, Sirtis was initially eager to dismiss comparisons between Troi and Spock, saying, "Some of Troi's character traits may be similar to his but Troi is not a Spock clone. She is a completely new character." The actress instead speculated that the Troi character was based on Gem, from . "I can only guess that the idea of that kind of character stuck in Gene Roddenberry's mind and that, when he was creating The Next Generation, he decided to use it," Sirtis theorized. (, issue 126, p. 46)

It was Gene Roddenberry who thought up the name "Deanna Troi". As a personal secret between himself and Susan Sackett, Roddenberry deliberately took the character's first name from Sackett's middle name, and Wesley Crusher's first name from his own middle name. ("Star Trek Redux: Log Entry 35", Inside Trek: My Secret Life with Star Trek Creator Gene Roddenberry)

In early brainstorming, the character of Troi was to have three breasts, but D.C. Fontana objected to this. She later recalled, "I felt women have enough trouble with two. And how are you going to line them up? Vertically, horizontally, or what? I was like, please, don't go there. And they didn't, fortunately." 

A character description of Deanna Troi was included in the first draft "bible" for Star Trek: The Next Generation (dated ). (Star Trek Creator: The Authorized Biography of Gene Roddenberry, paperback ed., p. 556) In that document, Troi was described as only a quarter Betazoid with some telepathic powers due to her "Starfleet officer grandfather having lived on Betazed with one of its humanoid females." Her past relationship with Riker was described as "intimate." ()

Troi's description in the original TNG casting call (dated  and reprinted in the ) was as follows:
"LT. DEANNA TROI – An alien woman who is tall (5'8-6') and slender, about 30 years old and quite beautiful. She serves as the starship's Chief Psychologist, Deanna is probably foreign (anywhere from Italian, Greek, Hungarian, Russian, Icelandic, etc.) with looks and accent to match. She and Number One are romantically involved. Her alien 'look' is still to be determined."

Despite having been described as a quarter Betazoid in the first draft TNG writer's guide, Troi's alien roots were not fully detailed in the casting call. This omission was presumably for the sake of simplicity. ()

In a revision of the series bible (dated ), Troi was no longer referred to as a lieutenant, but as a lieutenant commander. However, she was still described as the Enterprises chief psychologist. ()

Troi's position in one of the Enterprise-D's three center seats, the other two chairs occupied by Picard and Riker, was originally (i.e., on the eve of the 4 February revisions) to have been filled by Data. This was changed when the producers realized that Troi would be strengthened both in her shipboard role and as a character if she were to occupy the third central seat. Troi was also given the informal duty of notifying Picard of the concerns of his thousand-plus crew, a duty that was initially the official responsibility of Geordi La Forge. ()

In the final draft of the first season writer's guide (dated , most likely with the script for  under development), Troi's heritage was altered to how it is established in the series – half Betazoid, with her Starfleet father having lived on Betazed with her native mother. Also, the description of Troi's past romance with Riker was changed from "intimate" to "unconsummated." ()

In her book BFI TV Classics - Star Trek (p. 63), Ina Rae Hark suggested that Troi was created to counteract Picard's dispassion, as Hark supposed his emotional detachment would otherwise be problematic regarding his command decisions. "TNG resolves this dilemma by having Troi serve as a link between Picard's intellectual and scientific advisers and the more passionate field operatives," Hark observed. "She even has a seat on the bridge so that she can read the emotional nuances of potential adversaries for her emotionally tone-deaf captain."

Personification 
Deanna Troi was originally to have been played by Denise Crosby, while Marina Sirtis was auditioning for the role of Macha Hernandez, a character later to be named Natasha Yar. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 151) By , in fact, the only actress who seemed suitable to be cast as Troi was Crosby.  However, Crosby herself felt she struggled with the role, later expressing, "What was a Betazoid? It just sounded so gobbledygook and weird."  On 28 April 1987, a casting tape that included Susan Gibney auditioning for the part was sent from Bonnie Finnegan to TNG Casting Director Junie Lowry.

Although Producers Robert Justman and Rick Berman were happy with the arrangement of Troi being played by Denise Crosby and the security chief being played by Marina Sirtis, Gene Roddenberry decided that each of those two actresses would be better as the other's character, and the roles were consequently reversed, Roddenberry deciding Sirtis' appearance was a better fit for the alien Troi than for the Human security chief. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 151; ) Said Crosby, "From what I understand from the producers, they were sold on me, as that part [....] Gene felt that – now these are his words – that [...] Troi should be this exotic, otherworldly creature, and I was just this kind of American golden girl." ("Selected Crew Analysis: Casting", TNG Season 1 DVD special features) Furthermore, the producers decided that Sirtis brought a warmth and empathy to her audition that would work very well for the role of Troi. (Star Trek - Where No One Has Gone Before, paperback ed., p. 117) Upon learning she wouldn't be cast as the security chief, though, Sirtis at first suspected she had blown her chances of appearing in the series. (, issue 126, p. 48) "After my third audition for Tasha, I was literally walking out the door when they called me back to read for Deanna," Sirtis noted. (Trek: The Next Generation, 2nd ed., p. 27) The producers asked her to audition for the Troi role, thrust some script pages at Sirtis, and gave her an hour to learn three scenes. (, issue 126, p. 48) "While I was looking at the script," she continued, "Director Corey Allen came in and said, 'You have something personally that the character should have... an empathy, so use it." (Trek: The Next Generation, 2nd ed., p. 27) Looking back, Sirtis found that piece of advice "funny," as she didn't personally believe she herself was much like the character, having a more hot-headed temperament than Troi. At the time, though, she was encouraged by Allen's comments. Sirtis closed herself off in a room for the hour she had been given to prepare, during which the actress bore in mind that she typically never managed to audition while holding a piece of paper in her hands. "So, in that hour, I was determined to just memorize the scenes and tough it out," she remembered. "But my knees were knocking all the while and I was scared to death. I thought, 'OK, don't panic. Just learn it, put down the papers and see what develops." (, issue 126, pp. 46, 48 & 58)

Marina Sirtis was grateful that the part she was now trying out for had been changed to Troi. She clarified, "Basically, I just wanted the job! But I have to be honest; it suited me better when they swapped us over [...] because the scenes were so much more emotional and I could really let go. The way I was playing it was like Greek tragedy – I'm not saying that was the right way to go, but I like that kind of stuff, because I can get my teeth into it." ()

Marina Sirtis was cast as Troi on . ("Selected Crew Analysis: Casting", TNG Season 1 DVD special features) That day, she received the call informing her she had won the role, though she had been in the midst of packing to return to England that afternoon, as her visa had expired. The news consequently startled her. "I was ready to go when the phone rang and I was told I got the job. So I unpacked! I was so excited you would have had to scrape me off the ceiling!" Sirtis exclaimed. (Star Trek - Where No One Has Gone Before, paperback ed., pp. 117-118)

Troi's accent was devised by Marina Sirtis, who was actually born to Greek parents in North London. "I didn't want anyone to pin down my accent to any particular country," she revealed, "and being good at accents, the producers trusted me to come up with something appropriate." (Trek: The Next Generation, 2nd ed., p. 27) She explained further, "It was an Eastern European accent, which kind of started with the Tasha Yar auditions, 'cause she was supposed to be from Eastern Europe. Then, when they told me to make an accent up, from Betazed, I kind of just modified that Eastern Europe accent a bit. I based it on a friend of mine, who's actually Isreali." ("Selected Crew Analysis: Casting", TNG Season 1 DVD special features)

An unused look considered for Troi included a "skant" version of the Starfleet uniform and a severe bun hairstyle, as well as another hairstyle that was curly and high. (TNG Season 1 Blu-ray, "Stardate Revisited" special feature)

Introduction 

Owing to the complexity of Troi's character, the TNG producers were somewhat uncertain about how to handle the part right up to the filming of series pilot . (, issue 126, p. 46) Though Troi's rank of lieutenant commander wasn't established in that episode, Picard refers to Troi as "commander" in the very first scene. During an away mission in "Encounter at Farpoint", however, Riker mistakenly refers to her as "lieutenant", carried over from an earlier version of the script.  Also, with the advent of "Encounter at Farpoint", Troi became the first counselor to appear in a Star Trek series.

Coming from a theater background with very little knowledge of how to act in television productions, Marina Sirtis felt unsure about how to play Troi in "Encounter at Farpoint". "I didn't understand what I was doing; I had the impression that Troi was an open sore of emotions, but I wasn't aware that you didn't have to show emotion to get the message across," she conceded. () Sirtis' performance in "Encounter at Farpoint" wasn't influenced, whatsoever, by watching the footage of herself as she played the part; she and her castmates weren't allowed to see any dailies of their work on the episode until three days before it was to have its first public airing. At lunchtime three days prior to the cast screening, Sirtis commented, "The prospect of seeing myself in this show for the very first time is terrifying." (, issue 126, p. 46) Although she attended the screening, the actress wasn't proud of her performance in the episode. On the contrary, she later admitted, "I hated myself in the pilot." ()

The TNG producers' uncertainty about how to handle the depiction of Troi continued after the filming of "Encounter at Farpoint". (, issue 126, p. 46) Consequently, several differences exist between the pilot episode's depiction of Troi and her appearance in the subsequent series. "People watching the pilot and then the rest of the series will think they've cast two different people in the role," reckoned Marina Sirtis. "My character changed quite a bit between the pilot and the series. Particularly in looks." (, issue 126, p. 46)

The changes to Troi between the pilot and the series include the fact that she communicates telepathically with Riker in the pilot, but does not do so in the series, a lessening of her abilities that essentially avoided the emotional soliloquies that made actress Marina Sirtis cringe in "Encounter at Farpoint". () She explained, "The producers decided that it would be too limiting to the character to just go around feeling things all the time. So, they changed the level of Troi's powers." (, issue 126, p. 46)

Other differences were changes in Troi's hair and clothing. Her trademark hairstyles were usually achieved with a combination of Marina Sirtis' own hair and hairpieces. The only time her own hair was used without any hairpieces was in "Encounter at Farpoint".  Also, Troi wears a virtually unique "skant" Starfleet uniform in that episode, but is mostly adorned in more informal attire in the series. In the pilot, she wears her curly hair down and held back by a headband, but she appears with a severe bun hairstyle throughout the first season (echoing the earlier hairstyle tried out during preproduction). Accounting for the modifications, Marina Sirtis stated, "After the pilot was shot, the producers decided that the look didn't suit the character the way she was originally envisioned. They wanted something a bit more elegant and contained." (, issue 126, p. 46) The factors that inspired these stylistic changes were, in Sirtis' own words, that Troi was "cerebral and kind of elegant." (The Fifty-Year Mission: The Next 25 Years, p. 101) Yet another reason her look needed to be changed was that the actress, on the other hand, was too overweight. (Cinefantastique, Vol. 23, No. 2/3, p. 76) "If you go back to 'Encounter at Farpoint', where I was dressed in the cosmic cheerleader outfit with the ugliest go-go boots ever designed, I was about twenty pounds heavier. Imagine a potato with matchsticks sticking out of it, and that was my shape." (The Fifty-Year Mission: The Next 25 Years, p. 101) "Encounter at Farpoint" is the only time Troi wears a uniform with rank insignia for the first half of the TNG series.

Serialization 
As the first season got underway, Marina Sirtis noticed that Troi, now clad in a variety of low-cut casual duty outfits, had become less of an intellect than the actress had first been led to believe the character would be. "Unfortunately, [...] when I [...] got cleavage, she lost her brain matter," Sirtis lamented. "That was a shame [....] I lost weight over the years, and [...] how much cleavage I showed depended on which [costume] I wore, since they were all cut differently and some were lower than others." (The Fifty-Year Mission: The Next 25 Years, pp. 101 & 102) Through the rest of the first season, Sirtis' own hair was taken up, and the high bun was a hairpiece, added to give extra height for a demure look. 

Although Picard refers to Troi as "commander", as is the customary verbal address for a lieutenant commander in informal situations, in the very first scene of "Encounter at Farpoint", she is not referred to as holding that rank in any other episode of the first season. Her rank as lieutenant commander was ultimately first established by a bridge monitor that appears in the third Season 1 installment, .

Not only did Marina Sirtis feel that the change from the constantly emotional Troi in "Encounter at Farpoint" freed the character "to have more substance and scope", but the actress also liked how Troi continued to be developed as the first season went on. While the filming of  – the eighth Season 1 outing – neared completion, the actress related, "This show's writers have given me a great deal to do. I'm not just there when they need an empath. That would have gotten boring real fast. So far, I'm very pleased with the things they've given me to do." In particular, Sirtis was of the opinion that the fact Troi's advice was taken extremely seriously by Captain Picard contributed to an overall strong role of women in the then-new series. On the other hand, although there was discussion about Troi having to take command in a (never-produced) first season episode, Sirtis vetoed that idea, stipulating, "I'm the mental person. Deanna would be dangerous with that kind of power." Meanwhile, one difficulty Sirtis found in playing Troi was performing the scenes featuring the Enterprise shaking. "I've been pretty uncomfortable doing those scenes so far. I'm hoping it doesn't show," she laughed. (, issue 126, pp. 46, 48 & 58)

As the first season progressed, the writers struggled with Troi's character, believing her to be one of the hardest to write for. Marina Sirtis admitted, "I always felt that Deanna posed a big problem for the writers, that they never quite knew how to use her that effectively on the show." ) In fact, according to Sirtis, Troi was almost dropped from the series, as a result. "Because they gave her these empathic powers and she wasn't just a normal psychologist," the actress explained, "they went, 'Oh blimey, well if she can sense feelings and figure out what's going on, maybe she shouldn't be in this scene.' 'Okay, write her out.' That happened a lot, because in the first season I didn't have an office, I was just around. I remember one of the directors came up to me and said, 'You only have a couple of lines in this episode, so I told them to give you the week off and write you out.' I was like, 'Thanks very much, but that's residuals I won't be getting!' At one point I really did feel that they were thinking about losing me. I've got this from Majel [Barrett, Roddenberry's wife]. He came home one day and said, 'I think we've got one too many girls on the show,' and it didn't need a rocket scientist to work out that you need a doctor and a security chief but you don't really need a psychologist. So I had a very stressful first season, because I didn't know if I was going to have a job at the end of it." (SFX: The A-Z of Star Trek, p. 82)

When Denise Crosby and Beverly Crusher actress Gates McFadden left the series at the end of its first season, the decision was made to retain Marina Sirtis as Troi for the second season. "It was very ironic, because I was the one whose job was in danger," she commented. "Come the second season, I'm the only one left of the girls. The weight lifted off my shoulders at Jonathan Frakes' wedding, in the hiatus. Gene took me aside and said, 'The first episode of the new season is going to be a Troi episode,' and I literally just burst into tears. It was all uphill from there." Even though Dr. Pulaski was introduced at the start of the second season, Sirtis felt that plenty room was still made for the role of Troi in that season, given that Pulaski actress Diana Muldaur was from a different generation. "So I got to do all the young woman stuff," Sirtis noted. (SFX: The A-Z of Star Trek, p. 82)

Troi's rank as lieutenant commander was reestablished in Season 2, appearing on the observation room viewscreen when Dr. Pulaski demonstrates an image of Troi's unborn fetus in second season opener .

From that point on, Troi wore her hair long, in loose ringlets, and it was taken off her face, held in place by a headband. Again, this look was achieved by a combination of Marina Sirtis' own long, curly hair and hairpieces, which added extra volume and length. The hairpieces could also be styled before they were added to Sirtis' own hair, which cut down on preparation time. As the series proceeded, there were subsequent slight changes to Troi's hair. 

Marina Sirtis was delighted with the televised narratives concocted for Troi. "When they saw that I had range, I got great storylines – three or four good ones every year," she enthused. "I think it was [La Forge actor] LeVar [Burton] who said, 'Troi is the soul and the conscience on the Enterprise.' Consequently I got all the emotional stuff to do, which is my dream – that's what I love to do." (SFX: The A-Z of Star Trek, p. 82) Sirtis felt that Troi particularly started to become more developed in TNG Season 3. "Things definitely got better starting in the third season," the actress declared. "She became less decorative and more interesting." () Sirtis never felt secure in playing Troi until around the third or fourth season, by which time the character had become firmly established as a professional psychologist, so Troi's absences from the bridge could be accounted for by presuming she was meanwhile working in her office. ()

Troi didn't appear in all the third season installments she potentially could have. In the first draft of Season 3 outing , Troi was stranded on an alien planet along with Geordi La Forge. When they encountered a Romulan officer on the planet's surface, Troi incapacitated him. "I felt very excited about this," Sirtis related. "I finally got to do something interesting and different and, of course, when the final script came not only was I not on the planet, but I had one line at the end of the show – and that was actually cut." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 202)

To portray a supposed nude scene in , Marina Sirtis and Majel Barrett wore skimpy underwear, contrary to claims later made by Barrett, who alleged that both she herself and Sirtis had been fully naked. ()

As each day's production on TNG often continued into the early hours of the next day, Marina Sirtis was cautious about the filming of Troi's scenes. "I often wanted another take – but I didn't necessarily ask for one because the crew was always itching to get home," she explained. ()

By the end of the third season, Troi was the TNG main character that received the least attention from the series' writers. "The trouble with Troi is that because she's an empath you think she walks into a room and says, 'I feel pain.' That's a cliche," Michael Piller pointed out. As a result, the writers were continuing to find that writing for her was challenging. "It is difficult," admitted Ronald D. Moore, "because you run into a double trap of how much does she know and when. Especially when dealing with powerful aliens. It's unfortunate because the things she's had, she's been wonderful in." (Cinefantastique, Vol. 21, No. 2, p. 51)

At the start of the fourth season, developing Troi more was a goal that Jeri Taylor very much wanted to achieve. This was because Taylor thought Troi had been underused and therefore wanted to make her a more rounded and interesting character. At that point in the series, Marina Sirtis unhappily concurred with the opinion that Troi had been underutilized, citing her exclusion from "The Enemy" as an example. Michael Piller accepted that further developing Troi, together with the other main characters, was on the writing staffers' minds from the start of the season. However, he also argued, "I think the last two years have seen her develop a great deal and that does not mean it's sufficient or there shouldn't be more done, but I believe that she used to be a character who looked at the screen and said 'I sense anger out there' and we've given her a chance to actually do therapy, to do some very serious stories and make some critical contributions to the solutions or problems and really become a counselor in the best sense of the word. I don't really think that she's an underdeveloped character anymore. I feel very good about Troi. She's a really sexy lady who provides an enormous amount of emotional support to our other continuing characters." (Captains' Logs: The Unauthorized Complete Trek Voyages, pp. 201 & 202)

In a scene from the first draft script of fourth season outing , Troi stated, "I am half-Betazoid, half Human... Yes, and all woman." Immediately thereafter, Jono touched her breasts and Troi explained to him, "They're breasts. Infants nurse on them." ("Difficult Days: Log Entry 48", Inside Trek: My Secret Life with Star Trek Creator Gene Roddenberry)

It wasn't until fifth season installments  and  that Troi's lieutenant commander rank was mentioned again, following the visual reference to it in "The Child". Also in "Conundrum", Deanna's birthday is shown on-screen as being March , which happens to be Marina Sirtis' real birth date.

After Susan Sackett discovered she had been excommunicated by the TNG cast and crew at Gene Roddenberry's funeral (held on ), she felt as though the character of Troi was essentially being channeled through Marina Sirtis. "She seemed a lot like her character at that moment when I ran into her on my last day on the Paramount lot," Sackett reckoned. "Perhaps she was becoming an empath like Deanna Troi." ("All Good Things: Log Entry 59", Inside Trek: My Secret Life with Star Trek Creator Gene Roddenberry)

The slight changes to Troi's hairstyle stopped at the start of Season 6, when it was altered more significantly. This time, much of Marina Sirtis' own hair was styled more loosely around her face, with the ringlet curls hairpiece secured in a low ponytail. This style was seen for the first time in . As the season progressed, this style was changed in favor of another style which saw Troi's hair taken back off her face, but still styled in lower ringlets and without any headband. 

In an ultimately deleted scene from "Relics", Troi met Montgomery Scott. Owing to the scene deletion, it is not explained why, at the end of the episode, Troi gives Scott a kiss goodbye, as they never actually meet during the final edit of the episode until that moment.

In , Marina Sirtis had fun playing Troi in a Wild West holographic program. She especially enjoyed dressing up, and it allowed her the first opportunity to portray the character with a hint of comedy. ()

In sixth season outing , Troi finally appeared in a Starfleet uniform. Not since "Encounter at Farpoint" had she been shown wearing a uniform with rank insignia (although a fictional depiction of a uniformed Troi appears in ). She also ceased wearing hair decorations.

Marina Sirtis was wowed by how, in penultimate Season 6 offering , Troi manages to instruct Data and Geordi La Forge on Romulan engine functions. In response, the actress quipped, "Amazing how, when her cleavage disappears, Troi can do other things!" ()

For Season 7, Troi's hair was given another new look, with long, but softer, copper-colored waves, first seen in . Again, this was achieved by a combination of Marina Sirtis' long, straightened, copper-highlighted hair and a hairpiece to add volume. Troi's hairstyle also varied in Season 7 depending on whether she was on duty or not. When off duty, her hair was looser, and she wore it with bangs. 

Marina Sirtis didn't enjoy performing Troi's transformation into an amphibian in seventh season outing . Her dislike of the experience was because she hated prosthetics and water, yet the part required her to be exposed to both. ()

Several former TNG writing staffers have expressed criticisms about Troi. "A therapist on a ship full of characters that supposedly had gone beyond Human foibles and no longer succumbed to petty jealousy and anger? Why is there a therapist on board?" stated Brannon Braga. Naren Shankar agreed, "I couldn't understand it, especially coming from an immigrant family where nobody talks about their problems, ever. The notion of having an onboard psychiatrist was so weird. I was, like, 'What does she do all day? I don't understand.' She could look at the guy on the viewscreen who's angry and go, 'I think he's angry. He seems angry to me, Captain." Tracy Tormé admitted, "I'm not really sure that the Deanna Troi character ever fully worked for me. I liked Marina very much as a person, but that character was a little [too] soft for me and touchy-feely." Unfortunately for Sirtis, she felt likewise. (The Fifty-Year Mission: The Next 25 Years, pp. 100-101) Although she spoke approvingly about Troi being "so deep with that kind of insight into people," Sirtis also bemoaned the fact that it wasn't made clear on-screen that Troi was intended to be the most intellectual of the main characters. (Trek: The Next Generation, 2nd ed., p. 27; The Fifty-Year Mission: The Next 25 Years, p. 101) "There wasn't enough range in Troi," the actress complained. "All she seemed to be feeling was a lot of anguish." Hence, the TNG writing staffers tried to improve their writing of Troi for Sirtis' benefit. "Poor Marina," said Shankar, "we really tried to help her in the last few years of that show." (The Fifty-Year Mission: The Next 25 Years, p. 101) Sirtis appreciated their efforts, remarking shortly after the series ended, "Within the last one and a half seasons, I've become much happier with my character's development." ()

Of all the TNG main characters, Deanna Troi had the most number of changes to the look of her character throughout the series, in both costume and hairstyles. Those incremental stylistic changes were important to how Marina Sirtis portrayed Troi. Moreover, the actress, in retrospect, pointed out that the advances in the portrayal of Troi coincided with how women, in general, were characterized in Star Trek. () Sirtis noted that both Troi and Beverly Crusher were simultaneously in "positions of power" and "were in the caring profession, so we couldn't be too aggressive." () Despite Troi often doing the same kinds of things, the actress felt she was fortunate to play a character whom she regarded as essentially the "soul" or "conscience" of the Next Generation crew. () "To me, Troi was the nicest person aboard the Enterprise," Sirtis proclaimed, "because, instead of being wacky and zany, she was always understanding and sympathetic towards people." () Sirtis also considered herself lucky that Troi was possessed and transformed by so many different entities in the course of the series. ()

Marina Sirtis did have one regret about Troi, at the end of the series. "If I could really travel back through time and relive the TV series, I wouldn't give Deanna a foreign accent – even though her mother is a Betazoid," she conceded. Sirtis believed her foreign accent had been made a mockery of by the fact that Majel Barrett-Roddenberry had played Lwaxana Troi with a distinctly American accent. "But over the years, Deanna lost the [foreign] accent and sounded much more mid-Atlantic," Sirtis observed. ()

Reappearances 
For , Troi's hairstyle more resembled her off-duty look from Season 7, but this time the hairstyle was worn with her on-duty uniform. The hairpiece used was much longer, however, in much smoother waves than the style seen in Season 7. 

The depiction of Troi in Star Trek Generations extremely appealed to Marina Sirtis. "Steering the Enterprise was among the many things which I loved about Star Trek Generations," she reminisced. "It's something which Deanna had never done on the television show [....] [In the film,] I wanted to press the right buttons at the right time, so I sought advice from Brent Spiner (as Data, Spiner had often piloted the Enterprise on the TV series), who said, 'Marina, you're not playing the piano. You don't have to press a million buttons." ()

For Star Trek Generations, Marina Sirtis played Troi for about three weeks of the film's shoot, whereas filming the movie took fifty days. "Because Generations was obviously shot over a longer time period [than the TV series], I asked for that extra take if necessary," she clarified. By the time of the film, Troi's accent had changed so much from sounding foreign that Sirtis noted, "She tried very hard to sound completely American during Generations." ()

From  onwards, Marina Sirtis wore full wigs as Troi. The reason, again, was largely a production one. In Star Trek: First Contact, two wigs were used, one which resembled the Generations look but had caramel highlights, and a much flatter, long layered wig seen when Troi was on Earth. 

Acknowledging Patrick Stewart and Brent Spiner as the stars of the TNG films, Marina Sirtis had no aspirations for Troi to appear in a central role in any future Star Trek film, despite the character having centrally featured in the occasional TNG episode. Shortly after her work on Star Trek: First Contact, Sirtis mused, "We could make 10 ST:TNG movies, and I really don't feel that any of them would be about my character. I'll always be a supporting actress in Star Trek. And, that's actually fine with me if they continue to do what they've done on the last two films, which is to find me something new and different to do. If they continue like that, I'd be perfectly happy. Also, I wouldn't have the responsibility of carrying a whole movie, like Patrick does. No one will blame me if a ST:TNG movie ever doesn't make any money!" However, neither did Sirtis expect, at the time of that interview, to appear in  or  any time soon, though she later ended up making three appearances in the latter series. ()

In , a new long wig was used to give Troi a smooth, caramel-highlighted hairstyle. This wig was also used for her appearances in Star Trek: Voyager. 

In , another long wig was used, with highlights and layers. Sirtis has commented that, at the time the movies were made, her own hair was very similar to the wigs she wore but that production reasons meant she wore full wigs. 

Marina Sirtis believed that, over time, she was becalmed by portraying Troi. "The job was almost 15 years: seven years on the series, then four films," she pointed out. "During that time I was being Deanna more hours in the day than I was being Marina, and it did kinda rub off on me." (SFX: The A-Z of Star Trek, p. 83)

Ultimately, Troi became the most prominent example of a counselor in the Star Trek franchise. She also set a precedent that wasn't followed until Ezri Dax became the second counselor to appear in a Star Trek series, in DS9 Season 7.

Troi is one of four characters to appear in two series finales ( and ), the others being William T. Riker, Worf, and Miles O'Brien.

Reception and aftermath 
Attending multiple conventions and discovering that Troi was very popular with fans who went to such events inspired Marina Sirtis into becoming more secure in her job of portraying the character, in about the third or fourth season of TNG. () Some of the fans, though, wanted Troi to be more akin to the actress who played her. "Because the people who attend conventions are fans of Troi, I receive some positive feedback, but sometimes fans say, 'Why can't Troi be more like Marina? Marina's so much fun, but Troi is a little dull sometimes," relayed Sirtis. ()

Due to the low-cut costumes Marina Sirtis wore in the early days of the series, Troi became the sex symbol of Star Trek: The Next Generation. () An aspect of Troi's character that, in the first three seasons of the show, fascinated fans was the hint of a romance between her and Riker. (Cinefantastique, Vol. 21, No. 2, p. 51) According to Michael Dorn, the idea of Troi having a romance with Worf, when he lobbied for it at conventions, was popular too. As it turned out, though, Jeri Taylor stated about Troi's Season 7 relationship with Worf, "I've probably gotten more antagonistic mail on this than anything." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 284)

A wig believed to have been worn by Marina Sirtis or one of her doubles in the latter films was sold on the It's A Wrap! sale and auction on eBay.

Apocrypha 
In the novel Triangle: Imzadi II, set in mid-2371, Worf makes a marriage proposal to Troi and she accepts. However, after Riker and Commander Elizabeth Shelby rescue Troi and Worf's son, Alexander, from a hostage situation, Troi and Worf realize that they are too different to be married and that Troi still has feelings for Riker. The couple call off their engagement as a result.

In the novel The Battle of Betazed, Troi is involved in a successful attempt to liberate Betazed from the Dominion, following the events of .

In the Star Trek: Deep Space Nine - Millennium novel The War of the Prophets, Troi was ship's counselor on the USS Enterprise-F and was killed when the ship was destroyed in an alternate future 2388.

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