Parallels (episode)
After Worf returns from a bat'leth tournament, he is the only person who notices subtle changes on the Enterprise.

Summary

Teaser
Worf dictates a log entry while on a Type 6 shuttlecraft, the .

"Personal log, stardate 47391.2. I am returning from the bat'leth tournament on Forcas III. The conditions were difficult. Several contestants were maimed. But I was triumphant. I won Champion Standing."

He picks up a Klingon trophy.

"I am looking forward to resuming my duties aboard the Enterprise, however, I am anticipating a troubling situation."

Back on the Enterprise, Riker and Worf walk down a corridor. Worf carries his bat'leth and trophy as Riker tells him that they are returning to the Argus Array. The subspace telescope has stopped transmitting data for the third time that year. He wants Worf to start a long range scan when he notices Worf's attention wandering and remarks that the Klingon seems extremely tense, considering the fact that he has just returned from a vacation. Worf replies that today is his birthday. 

They reach Worf's quarters, but Worf is hesitant to enter. He cautiously looks around and Riker worriedly asks what's wrong. Worf is afraid that someone might have set up a surprise party for him. Riker says that he hates surprise parties and would never do something like that to him. Worf apologizes and Riker exits. Worf proudly studies his trophy, places it on a table and heads to the bedroom. Out of the darkness, happy shouts of "Surprise!" erupt. Lights come up and several crew members are revealed. As Deanna Troi and Beverly Crusher rush to kiss Worf, Riker comes in, puts a silly party hat on Worf's head and announces, "I love surprise parties!"

Act One
The guests sing "For He's a Jolly Good Fellow" modified with Klingon lyrics. During the song, Crusher arrives with a chocolate cake for Worf (with at least fifteen candles). Worf blows them out and complains that the song was not Klingon. Troi replies that it was not easy to translate; there seems to be no Klingon word for "jolly." Crusher offers Worf a knife to cut the cake. Riker explains to Worf that Captain Picard was needed on the bridge, but sends along his birthday wishes. Worf cuts a piece of the cake and offers it to Crusher, as Data arrives with a gift and presents it to Worf, who rips off the paper, revealing a colorful, abstract painting. He does not quite know what to make of it. Data explains that he has entered his expressionist phase and the painting is his interpretation of the Battle of HarOs. Worf is not impressed. Troi says that the painting is wonderful. She grabs it (turning it right-side up) and remarks, "And I know just where to put it". Riker takes down a shield from the wall and Troi hangs up the painting in its place. Worf is not pleased.

Geordi La Forge enters the party, sees the painting, and comments that it is nice. He approaches Worf, who suddenly feels dizzy. The Klingon thinks that Data's painting is making him dizzy. Crusher offers pieces of cake to La Forge, but now, strangely, it's a yellow cake instead of a chocolate one. Worf wonders about it aloud and Troi remarks, "Don't I wish."

Troi gives a present to Worf, saying that it is a gift from Alexander, who gave it to her before he left to visit Worf's parents. Worf opens it, revealing a cast of Alexander's forehead made into plaster. He proudly explains that it is "the ridges of a warrior." Troi says that Alexander wished to be at Worf's party and had "stayed up all night talking about how proud he was of his father." Worf thanks her for watching Alexander while he was away.

Suddenly, Worf hears Picard ask, "So, how old are you, Mr. Worf?" He turns and there Picard is, enjoying some cake. Worf is puzzled and says, "I was told that you could not attend." Smiling, Picard answers, "I wouldn't miss this for the world. How old are you?" Worf starts to tell the captain but stops himself. The guests wait eagerly for his response. Finally, he finishes by saying, "Old enough". Troi, Riker, and Picard laugh heartily.

In space, the Enterprise is stationary, positioned next to the gigantic Argus Array, a massive subspace telescope.

On the bridge, the senior staff man the primary stations as lower-ranking officers work the aft consoles. Picard demands a report from Lieutenant Commander Data, who tells the captain that the Array is working normally. Riker doesn't believe the android, as Starfleet reported that the Array had stopped transmitting data six days ago. Data explains that the Array is still sending data, but not to the Federation. He notes that the imaging systems have been re-directed. When Picard inquires where the information is being sent, Data replies that it is being directed to Sector 19658 and that he can't access the Array's main computer. Riker asks Worf about the sector. The Klingon reports that it is an uninhabited region, but there could be someone there receiving the data. Riker suggests beaming a repair team on board the Array, so they can download their imaging logs and find out where the information is being sent. Picard agrees with Riker, who exits the bridge with Data.

Meanwhile, Worf enters Ten Forward, which is full of busy officers. He soon notices Troi, sitting at a table. He goes to sit with her and tells her that he wants to talk about Alexander. He begins to say that it has never been easy for him to have the child on board. He has tried to be a good father and to give Alexander guidance. However, his son has his own mind about things. Troi replies that most children do. Worf continues by explaining that he could not have brought Alexander up without her and that sometimes she is like a mother to his son. Troi happily replies "That's one of the nicest things anyone has ever said to me." Worf reminds her about how he once asked Troi to watch over Alexander when he thought he was going to die after the spinal injury. He asks if she would like to formalize it. He wants Troi to be Alexander's Soh-chIm, a surrogate mother. Troi tells that it would be a great honor for her. Worf says that the closest approximation for a Soh-chIm would be his stepsister. Troi playfully remarks that it would make her mother Worf's stepmother. 

Worf's shocked reply is in a whisper: "I had not considered that." He thinks it over for a moment and says confidently, "It is a risk I'm willing to take." Just as Troi is accepting Worf's suggestion, Data asks Worf to accompany him to engineering. He leaves Troi happily sipping her drink.

Down in engineering, Worf, Data, La Forge, and Picard study the Array's imaging logs at the master systems display table. Data tells that the Array had been re-programmed to observe several Federation sites. From a monitor in the table, La Forge points out two space stations, Deep Space 5 and Starbase 47, and two planetary bases, Iadara colony and Utopia Planitia Fleet Yards on Mars. Picard notes that they are responsible for new starship development. Worf suggests that the array is being used to engage in covert surveillance of the Federation. Data tells that the Array was accessed six days ago. He shows a video of a Cardassian  cruiser approaching the station. La Forge says that the telescope is only three light years away from Cardassian space. Picard orders Worf to scan for Cardassians. La Forge offers a PADD to Worf and suddenly he feels dizzy again. When he regains his bearing, La Forge and Data have switched positions and Picard is gone. La Forge thinks that Worf should go to sickbay. He agrees.

At sickbay, Dr. Crusher asks if Worf has had any nausea or blurred vision as she scans him with a medical tricorder. Worf tells that he felt dizzy earlier that day at his birthday party. Crusher diagnoses him with the aftereffects of a concussion and offers vertazine medication for vertigo. As she is about to give him a hypospray, Worf stops her from administering it and tells her that he has no concussion. Crusher is puzzled and says that Worf came to sickbay that morning complaining about ringing in his ears. She asks if he doesn't remember it. Worf states he doesn't. Crusher says that Worf may have temporary memory loss resulting from the concussion. She tells Worf that he told her about how he lost the bat'leth tournament because someone hit him over the head. Worf says that he can prove definitively that he won the tournament.

They go to Worf's quarters where he finds a new trophy on the table. It has changed; it is now less decorated and reads "Ninth Place".

Act Two
Worf, angered now, thinks that someone is playing a trick on him. Crusher tries to calm him by explaining that memory loss can be very disorienting. Still agitated, Worf says that he recorded a log on his way back to the Enterprise. When accessed at a desktop monitor, the log plays out just as Worf dictated it while on his way back to the Enterprise for the first part of the log, but then Worf tells how someone used the illegal T'Gha maneuver on him and how the judges failed to notice it. He also presents the changed trophy to the camera. Then the log continues normally. Worf can't understand. Crusher still tries to convince him that he has lost his memory and again offers medication.

Meanwhile, the Enterprise still monitors the Argus Array.

On the bridge, Data asks Worf if he has finished the metallurgical scan of the Array. Worf can't remember being ordered to conduct such a scan. The tactical console alerts and Worf informs that a Galor-class ship is approaching. Picard orders to open a channel. He greets the captain and demand him to explain their presence on the Federation territory. The Cardassian, Gul Nador asks why the Enterprise is so close to the Cardassian border. Picard explains that they are repairing the telescope. Nador offers assistance but Picard declines the offer. Then Gul Nador inquires the purpose of the telescope. After Picard's explanation about scientific observation Nador adds: "I'm certain it would never be used to observe neighboring species." He gives his best wishes for the repairs but ends threateningly: "Just try to make sure that your studies are limited to astronomical phenomena." "Charming fellow," Riker notes.

Worf says that the ship was responsible for reprogramming the Argus Array. Picard doesn't know what he is talking about. As Worf explains seeing the ship at imaging logs, Picard is even more puzzled. Neither he nor Riker knows anything about the logs. Worf requests Data to show the logs, but like the others he doesn't know anything about them. Picard orders Data to re-examine the Array in case they would find evidence to support Worf's claims.

At Worf's quarters, Worf is agitated. Troi is present, wearing a blue dress. He tells that he remembers the logs very clearly. Troi doesn't believe what he is saying. She asks if he thinks that everyone else's memories have been altered. The door chime interrupts Worf. La Forge enters and says that they didn't find any signs of the Cardassian ship or any evidence of tampering from the logs. He thinks that the array simply suffered a mechanical failure. As Worf starts to speak, he once again nearly blacks out.

Things have changed again. Data's painting is on the opposite wall. Troi tells him that she hung it there at Worf's birthday party. As Worf looks back, the painting has changed to show a Klingon  starship. Now Troi wears her blue standard duty uniform and different hair style. As Worf's temper rises, La Forge takes his arm and suggests going to sickbay. Worf experiences another loss of orientation and finds himself standing at the bridge of the Enterprise. The ship is under red alert as Picard exclaims "Now!" to Worf as a Cardassian ship approaches.

Act Three
Worf doesn't know how to raise the shields, because the bridge and his console have been altered. The Enterprise is being fired upon and Data reports a direct hit to the engineering section and deck 42. The shield generators are overloading. After another hit, Picard orders Riker to take over the tactical station. He fires a spread of torpedoes at the Cardassian ship, damaging its main reactor. They return fire. Data reads from the Ops console that the Enterprises deflectors have sustained heavy damage and they have hull breaches on decks 17 and 36. Grimly, Picard orders Ensign Gates to take the ship away. Riker reports that the Cardassians have destroyed the Argus Array. Picard tries to contact La Forge at Engineering but gets Ensign  instead. He reports that La Forge has been taken to sickbay with plasma burns and that there is damage to the ship's secondary plasma conduits. Picard orders helm to lay in a course to Starbase 129. Then he demands an explanation for Worf's actions. Worf explains that he had "another memory loss." Riker doesn't understand and Worf informs Picard that he is not feeling well and requests permission to be relieved of duty. Picard grants it.

Worf goes to his quarters and finds still more changes. The Klingon ship painting is at the place where Data's painting originally was. On the table is an arrangement of white flowers. Worf accesses his computer terminal and searches for the log he recorded on the shuttlecraft Curie. The computer cannot find it. Worf asks for any log about the bat'leth tournament and gets a log about Worf having to repair the deflector and that he has asked his brother Kurn to take his place despite his lack of bat'leth experience. The door chime rings and Troi enters, wondering why he has locked the door. She questions his state of health and orders hot chocolate from the replicator. Worf asks if he can do anything for her and she responds playfully: "actually, there is."

She goes to sit on Worf's bed and asks him to join her. She lets his hair loose and starts to massage Worf's shoulders. She tries to get him talk and finally kisses his neck intimately. Worf is shocked and jumps away, talking about inappropriate behavior. To this Troi answers: "Even for your wife?"

Worf is mystified and mutters that things are changing. Troi asks what has changed. Worf explains: "I do not remember us, you and I, being mates. It is as if events, circumstances continue to change from moment to moment, but I am the only one who seems to be aware of it." Troi asks Worf if he really can't remember them becoming lovers and getting married during the past three years. Worf says that for what he remembers, they were friends, not lovers. Agitated and confused as he is, Troi promises to believe what he says and wants to help.

Down in engineering, Data initiates a subspace scan for temporal anomalies. More changes here; the warp core has a green dilithium chamber hatch and Data has completely normal-looking blue eyes instead of his usual yellow ones. Troi is called to sickbay and Worf questions Data about his relationship to Troi. He wants to know how long they have been married. "Two years, one month, twelve days", Data replies. According to him their relationship began when Worf was recovering from his spinal injury on Stardate 45587. Six months later, he asked permission from Riker to court Troi. Worf ponders aloud about the moment they "mated" for the first time. Data, taking this for an actual question, replies that he is not sure, but offers to investigate "when the initial coupling took place". Worf dismisses the offer, and Data reports no temporal anomalies on the sector. He suggests that they should try to pinpoint the moment when events became discontinuous. Worf recaps the changes he has experienced and Data thinks that they should try to find commonalities in those events. Worf realizes that La Forge was present on all occasions. Data decides to go to talk with him.

At sickbay, they are greeted by Doctor Alyssa Ogawa, with the rank of Commander. Beverly Crusher is nowhere to be seen. Sadly, she informs Data and Worf that La Forge has died from his injuries.

Act Four
Data examines La Forge's body with a tricorder, but he cannot find anything unusual, other than energy residuals from his plasma burns and the beginnings of ullar decomposition. Ogawa suggests that he should check the VISOR. As Data activates it using a diagnostic array, Worf faints to yet another change. He now wears a red uniform with a commander's rank pips and a differently-styled communicator. Doctor Crusher is standing on the spot where Ogawa was just a moment before. They inform him that he is the first officer of the Enterprise. 

Data (who now has his original eye color again) scans Worf and finds quantum flux in his ular RNA. Data goes to analyze the readings.

Data and Worf meet with Captain Riker in his ready room. Riker's trombone is there on display. Data explains that Worf's cellular RNA is asynchronous with normal matter. In essence, he doesn't belong there. This Data gives a lengthy explanation: all matter in the universe resonates on a quantum level with a unique signature. That signature is constant and cannot be changed through any known process. It is the basic foundation of existence. Data doesn't know the reason, but theorizes that Worf may originate from another quantum reality. The counterpart Riker thinks aloud that Worf's discontinuities started after he returned from the bat'leth tournament on the shuttle, which Worf confirms. Riker states that no shuttlecraft had left the Enterprise for over a month; despite this, they decide to follow Worf's course and search for any anomalies. As they prepare to leave, Worf asks: "How long have you been the captain of the Enterprise?" "Four years. Ever since Captain Picard was killed in the incident with the Borg." Worf closes his eyes in both frustration and distress over his captain's death. Riker observes that Worf doesn't seem to remember any of this. Worf tells the counterpart Riker that he does remember, only he remembers it differently.

On the bridge, the tactical officer – Lieutenant Wesley Crusher – reports a minor anomaly off the port bow in space. The bridge is even more modified now, with a transparent crosscut of the Enterprise separating the tactical and aft stations. The conn officer is a Cardassian ensign. Riker orders full stop and analysis, Data diagnoses the anomaly as a quantum fissure in the space-time continuum. 

Riker orders the anomaly to be viewed on main screen. A blue glowing rift appears after Data enhances it with a warp field. Data detects an ion trail intersecting the phenomenon. He says that is was left by a Federation Type 6 shuttlecraft. Data reports that he has an explanation.

In the observation lounge, Data is lecturing the senior officers. "I believe the quantum fissure is a fixed point across the space-time continuum. A 'keyhole' which intersects many other quantum realities." The counterpart Troi wants to know what they are and Data continues: "For any event there is an infinite number of possible outcomes. Our choices determine which outcome will follow. According to a theory, everything that can happen does happen in different quantum realities." Worf ponders that somehow he has been shifting from one reality to another. Troi asks how it happened. Data goes to the viewer and opens a diagram. "When Worf's shuttlecraft came into the fissure, its warp engines caused a small break between the quantum realities. Worf was thrown into quantum flux. He started shifting into other realities."

After the counterpart Dr. Crusher's question about La Forge's VISOR, Data says that the VISOR uses a subspace differential pulse which intensified the quantum flux. Worf wants to know how will they find his own reality. Lieutenant Crusher suggests using a subspace differential pulse to attempt to locate the quantum state that shares Worf's signature. Data agrees, "an excellent idea, lieutenant."

Worf and Troi return to Worf's quarters. Troi is depressed. She explains that she is afraid that her Worf will not return. She cannot believe that a reality exists where he never loved her. Worf tries comfort her by telling that he has always considered her a close friend. He assures that he would not be opposed of the possibility of a romantic relationship, although he has never really considered it. Troi continues, "what about our children?" In this particular universe, not only are Troi and Worf married, they have a two-year-old girl, Shannara, and a three-year-old boy, Eric-Christopher. She does not know anything about Alexander. The thought of Alexander not existing in this reality greatly upsets Worf and Troi rests herself on his chest. 

Meanwhile, the Enterprise scans the fissure with the subspace pulse.

On the bridge, the counterpart Wesley tells Worf that he has not found the correct reality after scanning over ten million frequencies. An alert sounds and Data reports a Bajoran ship approaching. Riker orders red alert, surprising Worf.

According to Troi, the Bajorans have become very aggressive since overpowering the Cardassian Empire. Riker adds that a day ago, they destroyed a subspace telescope because they thought the Federation was using it to spy against them. Crusher reports that the Bajorans are charging their weapons. Worf orders shields up as the ship is fired upon. Riker orders Crusher to return fire. Wesley reports that power system damage has caused an energy surge to the subspace pulse. The fissure is destabilizing. After another hit, the fissure lights up and several copies of the Enterprise appear. Data says from Ops station that the barriers between quantum realities are breaking down. In the space around them, more and more Enterprises appear.

Act Five

Wesley reports that the Bajorans are fleeing as Data says that quantum incursions are increasing exponentially. The sector will be completely filled with Enterprises within three days. The tactical console sounds wildly as they receive 285,000 hails. Riker quips that he wishes that he knew what to tell them, and asks Data how to stop the incursions. He theorizes: "Perhaps if we can find the ship that matches Worf's quantum signature. It was Worf's shuttle which traversed the fissure and weakened the barriers between quantum realities. If he re-enters the fissure in his shuttle and emits a broad spectrum warp field, it may seal the fissure."

Riker orders Crusher to send a general hail: "This is Captain Riker of the Enterprise – that is, the Enterprise that is indigenous to this universe. We've all encountered a quantum anomaly. We think we have found a way to return us all to our proper realities. But we need to find that ship which exhibits a certain quantum signature. Our Mr. Data will transmit that signature to you now." Data transmits the signature, but Wesley has difficulties finding out who is talking to who because of heavy communications traffic. Finally he receives a matching response. Riker orders the message on screen and the prime universe Enterprise bridge appears with Picard Prime, Riker Prime, and (presumably) a counterpart Worf at their stations. Riker on screen looks back to Worf, as if making sure that he is really there. Riker on the alternate Enterprise asks Picard Prime to send the shuttlecraft Curie. As Picard agrees, Riker terminates the comm by saying, with a degree of sadness in his voice: "It's good to see you again, Captain. It's been a long time." Picard glances questioningly at Riker Prime. 

The Enterprises continue to multiply in the sector with increasing speed.

In the shuttlebay, Data and several officers examine the shuttlecraft Curie. Data explains to Riker that he has modified the shuttle's engines to generate an inverse warp field. Worf asks if he will find himself near his Enterprise. According to Data, he may end up several days after or before the time he left because of the uncertainty principle. Riker gives his best wishes and leaves with the others, with only Worf and Troi remaining. They hug gently and finally kiss in a silent goodbye.

Worf sets away, but the shuttle is attacked by one of the Enterprises. Captain Riker hails it and he comes face to face with another alternate version of himself.

This counterpart Riker has a long beard, is disheveled and delirious, panicking on the badly-damaged bridge of his Enterprise. The transmission is filled with static. He begs not to be sent back to his own universe, where the Federation is gone, the Borg are everywhere and the Enterprise is one of the few remaining ships. However, Captain Riker says that there is no other option and if the plan works, everything will return to normal. Desperate and driven mad from exhaustion, the counterpart Riker declares they won't go back. He cuts the channel, then continues firing on the shuttle. Captain Riker quickly orders Wesley to disable that Enterprise. Wesley fires a single photon torpedo, collapsing the ship's weakened shields and engine core, which destroys it completely. They learn that the ship had already taken heavy damage, which resulted in their warp containment field being very weak; which Riker grimly speculates that the damage was due to constant fighting with the Borg.

As Worf initiates the inverse warp field, the inside of the shuttle is filled with dozens of ghost-like Worfs from other realities. The inside whites out, and Worf wakes up to find himself on the floor. He has returned to his normal rank and uniform. Worf contacts the Enterprise and Picard answers the hail. Worf, relieved to hear Picard's voice, asks the captain if everything is all right. Picard says that it is and then asks if there is a problem. Worf says no, but that he will explain when he returns to the Enterprise. Picard questions him about the bat'leth tournament. Worf, discovering the original trophy next to him, proudly replies that he has won "champion standing."

Worf and Riker walk and talk on the way to Worf's quarters. Worf has been telling Riker about what happened and assures him that the inverse warp field has sealed the rift so the quantum incursion will not be anything they have to worry about. Worf stops at the door and says, "I know what you are planning. I will not be surprised." Riker says he doesn't know what Worf is talking about but Worf does not believe him. Worf then enters his quarters just like he had when he returned the first time and he hurries to check the bedroom. Although there is no one there, he is startled as Troi steps into the room with a friendly "Welcome home, Worf!" After she explains that she was simply caring for Alexander's hissing beetle while both Worf and Alexander are away, Worf asks if she lives there. When she asks what that's supposed to mean, Worf adds, "It is a long story."

Troi presents him with a gift and says that Riker wanted to throw him a surprise party but she talked him out of it, to which Worf is grateful. Troi says that she knows Klingons like to be alone on their birthday. "You probably want to meditate or hit yourself with a painstik, or something." As she is about to leave, Worf asks her to join him for dinner and she accepts. He pauses at the replicator and, perhaps momentarily thinking about the counterpart Troi from the last reality that he encountered, orders champagne from the replicator, and Troi's face adopts a curious expression, presumably confusion at his actions and her empathic knowledge.

Memorable quotes
"That was not a Klingon song!"
"It wasn't easy to translate. There doesn't seem to be a Klingon word for "jolly"."
 - Worf to Troi, after he is serenaded by his birthday guests with the Klingon version of "For He's a Jolly Good Fellow"

"I believe the quantum fissure we discovered is a fixed point across the space-time continuum. A keyhole which intersects many other quantum realities."
"What do you mean, quantum realities?"
"For any event, there is an infinite number of possible outcomes. Our choices determine which outcomes will follow. But there is a theory in quantum physics that all possibilities that can happen or could happen do happen in alternate quantum realities."
"And somehow, I've been shifting from one reality to another."
"That is correct."
 - A counterpart of Data, a counterpart of Deanna Troi, and Worf of the prime universe

"This is Captain Riker of the Enterprise. That is, the Enterprise that is indigenous to this universe. We've all encountered a quantum anomaly. We think we have found a way to return us all to our proper realities, but we need to find that ship which exhibits a certain quantum signature. Our Mr. Data will transmit that signature to you now."
 - A counterpart of Captain William Riker of the current reality

"I was in sickbay. Doctor Crusher told me I had a concussion, but I do not remember that happening."
"Think back. Are you certain that was the very first change?"
"Before. Yes. Yes, I was in engineering. I felt a wave of dizziness and when I looked up, you and Commander La Forge were on the opposite side of the room. And Captain Picard was gone. I thought I had blacked out for a moment and had not observed your movements. And at my birthday party, the cake was chocolate and then it was yellow. And Commander Riker told me Captain Picard was not going to attend, and then suddenly he was there."
- Worf Prime and a counterpart of Data

"Captain, we're receiving 285,000 hails."
 - A counterpart of Lt. Wesley Crusher, as a huge number of Enterprises appear

"At this rate, the sector will be completely filled with Enterprises within three days."
 - A counterpart of Lt. Cmdr. Data, as Enterprises continue to pour into the region

"We won't go back. You don't know what it's like in our universe. The Federation's gone! The Borg is everywhere! We're one of the last ships left. Please… you've got to help us!"
"I'm sorry, there's no choice. If this works, everything will return to…"
"NO, WE WON'T GO BACK!!!"
 - A counterpart of Captain William Riker, panicking on the bridge of an alternate Enterprise, and Captain William Riker of the current reality

"Captain, it appears that we have found the quantum signature you are looking for."
"Data believes that by sending Worf back through the fissure again, it would return us all to our proper realities."
"Our Data has said the same thing."
"We need you to send us your shuttlecraft, Curie."
"We're launching it now."
"Thank you. It's good to see you again, Captain. It's been a long time."
 - Captain Jean-Luc Picard of the prime universe and a counterpart Captain William Riker of the current reality

"You don't remember any of this, do you?" 
"I do remember. I just remember differently."
- A counterpart Riker and Worf

"Welcome home, Worf! I hope you don't mind, I let myself in. I promised Alexander I'd feed his Dalvin hissing beetle while you were both away."
"So you do not live here?"
"What's that supposed to mean?"
- Deanna Troi Prime and Worf, after Worf returns to his quarters in the prime universe

"How was the bat'leth tournament?"
"It was fine, sir. I won Champion Standing."
 - Picard, to Worf after he returns to his reality

"I know Klingons like to be alone on their birthdays. You probably want to meditate, or hit yourself with a painstick, or something."
- Deanna Troi, to Worf

Background information

Production history 
 First draft script: 
 Final draft script:  
 Premiere airdate: 
 First UK airdate:

Story and production 

 It was originally planned that Tasha Yar would be featured in the alternate timelines that Worf experienced, but it was decided that this would make the episode too similar to . Therefore, Wesley was included instead. Brannon Braga commented, "Wesley could have been explored in more depth, but I thought it would just be more interesting if he were just there." (Captains' Logs: The Unauthorized Complete Trek Voyages)
 This episode is the first to suggest a relationship between Worf and Counselor Troi, which grew throughout the remainder of the season. The events of , albeit a parallel universe's version of those events, are referenced as the catalyst for their relationship. Brannon Braga noted that the writers had been placing hints at a possible relationship since Season Five. "I think most people didn't pick up on the relationship we were trying to evolve, which was good – we wanted that surprise when we find out they're married." () In commentary for the episode released on the DVD Star Trek: Fan Collective - Alternate Realities and also included on the TNG Season 7 Blu-ray release, Braga stated that the romance between the two was initially conceived as a joke among the writing staff, but upon seeing the dailies, it was felt that the two actors had really good chemistry with each other.
 On the "Worf-Troi thing", Jeri Taylor commented, "It's been kinda fun, but it infuriates some people. Some people are so upset that we didn't put Riker and Troi together and just get it over with, and how dare we introduce this!" ()
 Noting the future incarnations of the relationship, Braga observed, "This is a couple that only has relationships in alternate realities and timelines… even as creatures. They make normal couples look boring by comparison!" ()

 The last line of the episode – "Champagne" – was unscripted. It was added by Jeri Taylor after director Robert Wiemer asked for a more definitive ending. ()
 Braga noted that he was careful to downplay the idea that the alternate realities could be a result of Worf losing his mind to avoid similarities with . (Captains' Logs: The Unauthorized Complete Trek Voyages)
 It was originally planned that the crew would sing "Happy Birthday" to Worf in Klingonese, but the producers decided it was not worth paying the fee demanded by the song's royalty holders. () "For He's a Jolly Good Fellow" was substituted instead. In the commentary for the episode, Braga stated that this had the fortunate circumstance of allowing him to write the quip about there not being a Klingon word for "jolly."
 In the "First Officer Worf" reality, a Cardassian ensign is seen at the helm of the Enterprise, marking the only appearance of a Cardassian wearing a Starfleet uniform. The  suggests that the roles of the Bajorans and Cardassians were reversed relative to their roles in the "real" universe.

Reception
Jonathan Frakes disliked the Worf-Troi relationship started in "Parallels", commenting "The Worf/Troi idea is just absurd! It makes for great material at conventions but for real character development I think it's ridiculous". ("Looking Out for Number One", )
In his commentary for the episode, writer Brannon Braga discussed the use of technobabble within the episode. While he felt that the explanation as why Worf shifted realities came off well, he was less-than-pleased with the solution for returning him, citing Wesley Crusher's line that "We could scan the quantum fissure using a subspace differential pulse" as a piece of technobabble that didn't work well and which he didn't really understand. Despite this, he felt that the rest of the episode worked well enough that it could be gotten away with.

Continuity 
 This episode takes place on the same stardate as , which was broadcast the same week.
 During the course of the episode, Deanna Troi wears most of her wardrobe of costumes from the past six seasons, including the dress featured in one of Reginald Barclay's holodeck programs. The only costume she does not wear is her uniform from  (which she later wore again in ), her first season dark attire, and her gray and purple jumpsuit.
 This episode marks the first time Worf appears in a command red  since . He later returned to wearing a red Starfleet uniform beginning with . 
 Many of the alterations made to the bridge in this episode were reused on the future Enterprise-D in .
 The combadge from the universe where Worf is first officer shares the same design as the imaginary future simulation from .
 Data's eye color changes from yellow to blue and back again between universes. In commentary, writer Brannon Braga commented that this was something that he had not written and thought a nice touch upon seeing the episode.
 This episode establishes that Federation starship development takes place at the following locations: Deep Space 5, Starbase 47, the Iadara colony, and the Utopia Planitia Fleet Yards on Mars. The Drafting Room 5 at Utopia Planitia is shown as a simulation in the Enterprises holodeck in , when La Forge studies the work of Dr. Leah Brahms, the engineer who designed the warp engines of the Enterprise-D. The simulation is run again in .
 This episode was cited by Roberto Orci as providing the scientific rationale for the continued existence of both the prime reality and the alternate reality in the 2009 film . 
 Worf's trophy can be seen again during the dinner scene in the  episode .
 The Argus Array previously appeared in  where it was defective due to an alien probe.

Sets and props 
 The wall decoration seen in the observation lounge in one of the quantum realities was also seen in Proconsul Neral's office in the fifth season episodes  and , in Mr. Mot's barbershop in the sixth season episode , in the reception area at Arkaria Base in the sixth season episode , in the office of Minister Kray in the  first season episode , in Neelix's quarters in the episode , and in Annorax ready room aboard the Krenim weapon ship in the VOY fourth season episode .
 The chair in Worf's quarters was also seen in the episodes , , , , , , , , , and  and was used as the command chair aboard the Tarellian starship in the first season episode . It was designed by Peter Opsvik. 
 Worf's quarters also feature the statue of Kahless and Morath which was previously seen in the episodes , , , and  and will later be seen in  and  and in the video game Star Trek: Klingon.
 Before Worf enters his quarters in the teaser, a voice can faintly be heard saying "Surprise!". It is unclear if this is a blooper or intentional.

Apocrypha 
 In the TNG Pocket novel , Q implies that he was responsible for sending Worf into the alternate universes, since he foresaw that Worf would need the experience to rescue Picard from "Them."
 In the novel Q-Squared, set shortly after these events, Worf notes that he has not told any of his shipmates about the world he witnessed where the Borg had all but conquered the Federation because he found the implications of what had happened to his friends and family in that world to be too uncomfortable. 
 Some alternate realities were explored in the novel series Star Trek: Myriad Universes.
 A variation on the timeline encountered by Worf where Picard died during his time as Locutus of Borg is depicted in the novel Headlong Flight, although it includes other differences such as Pulaski still being the ship's CMO during the confrontation with Locutus and Natasha Yar still being alive.

Video and DVD releases 
 UK VHS release (two-episode tapes, CIC Video): Volume 81, catalog number VHR 2861, 
 As part of the UK VHS collection Star Trek: The Next Generation - 10th Anniversary Collector's Edition under the "Worf" section, 
 As part of the TNG Season 7 DVD collection
 As part of the Star Trek: Fan Collective - Alternate Realities collection

Links and references

Starring 
 Patrick Stewart as Capt. Jean-Luc Picard
 Jonathan Frakes as Cmdr. William T. Riker

Also starring 
 LeVar Burton as Lt. Cmdr. Geordi La Forge
 Michael Dorn as Lieutenant Worf
 Gates McFadden as Dr. Beverly Crusher
 Marina Sirtis as Counselor Deanna Troi
 Brent Spiner as Lt. Commander Data

Special appearance by 

 Wil Wheaton as Wesley Crusher

Guest star 
 Patti Yasutake as Alyssa Ogawa

Co-stars 
 Mark Bramhall as Gul Nador
 Majel Barrett as Computer Voice

Uncredited co-stars 
 David Keith Anderson as Armstrong
 Michael Braveheart as Martinez
 Debbie David as Russell
 Cameron as Kellogg
 Tracee Lee Cocco as Jae
 Elliot Durant III as operations division ensign
 Gunnel Eriksson as science division officer
 Holiday Freeman as command division officer
 Kevin Grover as Cardassian helmsman
 Bill Hagy as operations division officer
 Fumiko Hamada as command division officer
 Gary Hunter as science division officer
 Kathy as Towles
 Lorine Mendell as Diana Giddings
 Michael Moorehead as science division ensign
 Joycelyn Robinson as Gates
 John Tampoya as operations division ensign
 Oliver Theess as command division officer
 Mikki Val as operations division officer
 Guy Vardaman as Darien Wallace
 Christina Wegler Miles as command division ensign
 Unknown performers as
 Female civilian
 Female science division officer
 Gates (voice)
 Hayes (voice)
 Operations division officer
 Ten Forward waiter

Stand-ins 
 David Keith Anderson – stand-in for LeVar Burton
 Debbie David – stand-in for Brent Spiner
 Michael Echols – stand-in for Michael Dorn
 Nora Leonhardt – stand-in for Marina Sirtis
 Lorine Mendell – stand-in for Gates McFadden
 Richard Sarstedt – stand-in for Jonathan Frakes
 Dennis Tracy – stand-in for Patrick Stewart

References 
47; 2366; 2367; 2368; analogy; Argus Array; astronomical phenomena; Bajoran; Bajoran ship; bat'leth competition; Battle of HarOs; birthday cake; birthday party; blurred vision; Borg; broad-spectrum warp field; Champion Standing; Cardassian; Cardassian border; Cardassian Empire; Cardassian space; imprint; cellular; champagne; chocolate; chocolate cake; concussion; ; ; Dalvin hissing beetle; day; decomposition; Deep Space 5 (); diagnostic array; dizziness; Eric-Christopher; expressionist; Federation; Federation territory; "For He's a Jolly Good Fellow"; Forcas III;  (starship); Galaxy class decks; ; gift; hot chocolate; hypospray; Iadara colony; imaging log; Interspecies reproduction; inverse warp field; ion trail; Klingon; Klingonese; Kurn; maimed; metallurgical scan; Nador's starship; nausea; number one; PADD; painting; patient; phenomenon; plasma burn; quantum fissure; quantum fissure system; quantum flux; quantum incursion sector; quantum level; quantum physics; quantum reality; quantum signature; red alert; RNA; ; ; ; secondary plasma conduit; Sector 19658; Shannara; shield generator; shore leave; social gathering; Soh-chIm; space-time continuum; Starbase 47 (); Starbase 129; Starfleet; stepsister; stepmother; subatomic level; subspace differential pulse; subspace relay station; subspace scan; surprise party; surrogate mother; T'Gha maneuver; temporal anomaly; type 6 shuttlecraft; ; trombone; trophy; universe; uncertainty principle; Utopia Planitia Fleet Yards; ; vertazine; VISOR; warp containment field; warp field; yellow

Other References 
Shuttlebay Operations: Ansel Adams; approach vector; ; Chris Pike; Clarke; ; ; ; Decartes; ; El Baz; ; ; Hangar 2; Hangar 3; Hangar 4; Hangar 5; Heinlein; Indiana Jones; JF Kennedy; Lindberg; main shuttlebay; McAuliffe; Onizuka; PT Farnsworth; primary acquisition zone; refit; Sakharov; ; Shuttlebay 3; Starbase 515; ; tractor control zone; Type 7 shuttlecraft; Type 15 shuttlepod; Von Braun

External links
 
 
 
 

de:Parallelen
es:Parallels
fr:Parallels (épisode)
ja:無限のパラレル・ワールド（エピソード）
nl:Parallels
TNG episodes