Star Trek crossovers

Several characters within the "Star Trek" franchise, primary and secondary, often made crossover appearances between one series and another. This included appearances of established characters on premiere episodes of new series, a few long-term transfers from one series to another, and even crossovers between "Trek" films and television. A few crossover appearances, such as that of Spock on ' and the time-travel of the crew of ' to the era of "" were especially lauded by both fans and critics.
Appearances in series premieres.
After "The Original Series", at least one character from an earlier series appeared in the premiere episode of each new series. These were the appearances of most of the ' main cast in "", the first episode of '; Leonard McCoy in "Encounter at Farpoint", the first episode of "The Next Generation"; Captain Jean-Luc Picard and Miles O'Brien in "", the first episode of "Deep Space Nine"; Quark and Morn in ", the premiere of '; Zefram Cochrane (from the original series episode " and the film ') in "", the premiere of "Enterprise"; Sarek in "The Vulcan Hello", the first episode of '; Sylvia Tilly in "Runaway", the first episode of '; Jean-Luc Picard and Data in "Remembrance", the first episode of "; NOMAD (from the original series episode ") in "Second Contact", the premiere of "," and Nyota Uhura in "Strange New Worlds", the premiere of "."
Long-term transitions.
Two long-term transitions were the transfer of Worf and Miles O'Brien from permanent characters on "The Next Generation" to permanent characters on "Deep Space Nine". Worf stayed on "The Next Generation" until its conclusion, then transferred from the start of season 4 of "DS9". Chief O'Brien had appeared in fifty episodes of "The Next Generation", but only gained opening credits billing on "DS9", in which he appeared in almost every episode of all seven seasons. While not seen as often as Chief O'Brien, his wife Keiko O'Brien also transitioned as a series regular guest star from "The Next Generation" to "Deep Space Nine", bringing their daughter Molly. Miles O'Brien reprised his "Next Generation" role in that series' finale "".
Episodes and films focused on crossovers.
Television-to-television crossover.
An especially significant crossover is Spock's appearance on the two-part "Next Generation" episode "". Spock meets Data and they exchange opinions on the relative value of logic and emotion, and share mutual impressions of "Next Generation"s Captain Picard (who for Spock is a model of logical behavior, and for Data is a model of what it means to be human). Critics such as Ina Rae Hark have noted this encounter between two non-human characters in which they summarize their contrasting attitudes to humanity, Data embodying Spock's ideal of pure logic, while Data aspires to be more human.
Scotty appears in TNG Season 6, Episode 4 "".
Recycled footage from the original series episode "The Trouble with Tribbles" is used extensively in "Deep Space Nine"s time-travel episode "Trials and Tribble-ations". In addition to extensive archival footage of cast from the original series, actor Charlie Brill (portraying Klingon spy Arne Darvin) appears in both new and archival footage. The episode was designed to coincide with the 30th anniversary of the original series. Critic Matthew Kappell notes that the new episode simultaneously "parodies and valorizes" the original series, highlighting the discontinuities between two eras of "Trek" while trying simultaneously to weave them together.
William Riker and Deanna Troi from "The Next Generation" appear in a flash-forward to the future in "These Are the Voyages...", the final episode of "Enterprise". This episode was widely criticized by both cast members and fans for playing more like a "Next Generation" episode to the point of being an inappropriate wrap-up for the series.
Film-to-television crossover.
In the "Voyager" episode "", events from the film "Star Trek VI: The Undiscovered Country" (1991) play a pivotal role, and are reenacted with the same actors, thus allowing George Takei to reprise his role as Hikaru Sulu. The episode contains the added revelation that the character of Tuvok was on Sulu's ship "Excelsior" at the time. Critic Lincoln Geraghty cites this as an example of "Star Trek"s ongoing propensity for reverential recognition of earlier versions of the series. In bit of rather glaring discontinuity, the character of Lieutenant Dimitri Valtane is shown to be both alive at the end of the film and dead in the episode. Actor Tim Russ, who portrayed Tuvok, also made an appearance as a bridge officer from the same fictional time period, serving on the "Enterprise"-B in the feature film Star Trek Generations (1994).
Television-to-film crossover.
The film "Star Trek Generations" brought Kirk and Picard, "Enterprise" captains from different centuries, together to defeat a common enemy. It also marked the passing of the film franchise from the original series cast to that of "The Next Generation".
Characters more prominent on subsequent series.
A few occasional recurring characters introduced in one series continued into other series, sometimes attaining more significant roles in their subsequent "Trek" series than in the one in which they were first introduced:
All crossovers.
Character crossovers.
"The Original Series" on "The Next Generation" series of films
The Original Series on Enterprise
The Original Series" on "Star Trek (2009), Star Trek Into Darkness (2013), Star Trek: Beyond (2016)
The Original Series" on "Short Treks
Actor crossovers.
The Original Series on The Next Generation, Deep Space Nine and Voyager:
The Original Series on Deep Space Nine:
Clint Howard who played Balok on the episode “The Corbomite Maneuver” appeared as the mentally ill Sanctuary resident Grady in DS9’s “Past Tense, Part II”
The Original Series on Enterprise:
Clint Howard who played Balok on the episode “The Corbomite Maneuver” played the ferengi Muk in Enterprise’s first-year episode “”
The Original Series on Discovery:
Clint Howard who played Balok on the episode “The Corbomite Maneuver” played an Orion Drug Dealer in the "Star Trek: Discovery" season one finale, "Will You Take My Hand?"
Intercompany crossovers.
"Star Trek" has had a few intercompany crossover stories in comic books. These include:
Marvel Comics franchise, "X-Men"
DC Comics franchise, "Legion of Super-Heroes"
IDW Publishing, "Doctor Who"
Boom! Studios, "Planet of the Apes"
DC Comics franchise, "Green Lantern"
Dark Horse Comics, "Alien"
IDW Publishing, "Transformers"
CCG intercompany crossover scenario.
Lucasfilm franchise, "Star Wars"
Parody crossovers.
In Turkish comedy "Turist Ömer Uzay Yolunda" (Turkish: "Ömer the Tourist in Star Trek"), produced and directed by Hulki Saner, titular hobo (cult turkish character, Turist Ömer played by Sadri Alışık) is beamed aboard the Starship Enterprise.
In Polish cabaret sketch of Kabaret Moralnego Niepokoju (Polish: "Cabaret of Moral Anxiety") - "Bajki: Przygody pilota Pirxa", titular hero (taken from Stanisław Lem "Tales of Pirx the Pilot"), and his companions, wears era Starfleet uniforms. "Star Trek" style technobabble is also in use.