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 The Next Generation and the time-travel of the crew of Deep Space Nine to the era of The Original Series were especially lauded by both fans and critics.
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 "All Good Things...".
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 "Unification". 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 embodies Spock's ideal of pure logic, even as he aspires to become more human.[1]
Scotty appears in TNG Season 6, Episode 4 "Relics".
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.[2]
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.[3][4]
In the Voyager episode "Flashback", 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.[6] In a 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:
Spock's father Sarek appeared in only one episode of the original series, but became a more developed character in three movies and appeared in the Next Generation episode named after him and the first part of "Unification". Sarek's appearance in the former is described in The Star Trek: The Next Generation Companion as "the first major unifying event tying together the old and new Trek eras since McCoy's cameo" in the original series.[7] Sarek later appeared in Star Trek: Discovery.
Recurring character Q, originally introduced in the premiere episode of Next Generation, continued to appear in episodes of Deep Space Nine, Voyager, Lower Decks and Picard. Teleplay writer Robert Wolfe found it difficult to incorporate Q into the DS9 universe as the character had been conceived so much as a foil for Captain Picard. He eventually decided to use Q to show personality differences between Picard and Sisko.[8] It was also difficult to decide how to introduce Q into Voyager, as it was necessary to explain why Q did not return the ship to Federation territory.[9]
Although appearing in only five episodes of The Next Generation and six episodes of Voyager, the character of Reginald Barclay became quite pivotal to the story-arc of the final season of Voyager, significantly contributing to the reestablishment of contact between the ship Voyager and the Federation. Barclay also appears in a cameo role in the eighth movie in the film series, Star Trek: First Contact.
Three Klingon characters from separate individual episodes of the original series, Kor, Koloth and Kang, all appear in the Deep Space Nine episode "Blood Oath", and Kor further appeared in DS9 episodes "The Sword of Kahless" and "Once More Unto the Breach". Crew members who worked on "Blood Oath" felt that a "special connection" was being made to the original series.[10] Kang made an additional cameo appearance on Voyager, verbally dueling with Captain Sulu in a brief scene of the episode "Flashback".
The two Ferengi, Arridor and Kol, were minor characters in the TNG episode "The Price" but were the principal antagonists in the Voyager episode "False Profits".
The Borg race appeared in six of the StarTrek series. Introduced in The Next Generation, they would appear in Deep Space Nine, Voyager,Enterprise,Picard, and Prodigy. Their role in Deep Space Nine was limited to an appearance in the premiere episode to explore Benjamin Sisko's troubled past (his wife having been killed in a major confrontation with the Borg), while their role in the Enterprise episode "Regeneration" served as a 'sequel' to Star Trek: First Contact, as an archaeological expedition discovers the remains of the time-travelling Borg sphere that was destroyed in First Contact and unwittingly reactivate a pair of Borg drones. However, the Borg became a recurring threat on Voyager. One crossover character was the Borg Queen first introduced in the Next Generation feature film Star Trek: First Contact. She would then become a recurring character on Voyager appearing in the two-part episodes "Dark Frontier" and "Unimatrix Zero" and in the series finale "Endgame". These episodes form a narrative thread in which the Borg Queen is battling with Janeway in attempts to re-assimilate Seven of Nine.[11] Only in the final Voyager episode is the Borg Queen played by the same actress who played her in the feature film Star Trek: First Contact, Alice Krige. The magazine Cinefantastique described Krige's appearance as the highlight of this episode.[12] Eventually a new, cloaked form of the Borg Queen appears in Star Trek: Picard, quickly followed by a version more reminiscent of the appearance and personality of the character seen in First Contact and Voyager, in an alternate timeline. Another crossover character is Hugh, a Borg drone who appeared in the TNG episode I, Borg and subsequently in the first season of Picard.
The Original Series on Star Trek (2009), Star Trek Into Darkness (2013), Star Trek: Beyond (2016)
Aside from a complete recasting of all the primary roles from the original series, the reboot Star Trek film series also specifically brought back Leonard Nimoy to reprise his role as Spock last seen in Star Trek VI: The Undiscovered Country for the first two films in the reboot series. A recast Sarek, a recasting of Spock's mother Amanda (Winona Ryder), and a recast Captain Pike also appears in Star Trek (2009).
Nimoy's Ambassador Spock, and the rest of the original series cast reappear in holographic (Spock) and photographic form in Star Trek: Beyond (2016) and have no speaking roles.
The Original Series on Discovery
The characters Sarek, Amanda Grayson, Spock, Christopher Pike, Number One and Harry Mudd from The Original Series appear as recurring characters in Discovery, all played by different actors. The Talosians and Vina, from the unaired pilot of the original series "The Cage" and the two-part original series episode "The Menagerie," also appeared in the Discovery episode "If Memory Serves". Archival footage from "The Cage" was also used in "If Memory Serves", with archive footage of Leonard Nimoy as Spock from the episode "Unification II" being used in the Discovery episode "Unification III"
The Guardian of Forever appears in both parts of the episode "Terra Firma", though it is only revealed to be the Guardian in the second part. The character last appeared in "Yesteryear", an episode of The Animated Series.
The Original Series on Short Treks
Harry Mudd appears in the episode "The Escape Artist"
The character of Christopher Pike returns for three Short Treks episodes, "The Trouble with Edward", "Ask Not" and "Q&A", with Spock and Number One appearing in the latter two episodes
NOMAD (from the original series episode "The Changeling") appears in a storage room in "Second Contact"
The characters Spock and James T. Kirk are depicted in their Animated Series form for a brief, mute cameo in the first season finale "No Small Parts", with Landru from "Return of the Archons" also making a brief appearance.
Hikaru Sulu appears as a hallucination in the episode "Crisis Point 2: Paradoxus."
The Original Series on Strange New Worlds
The characters Spock, Christopher Pike, Number One, Nyota Uhura, Christine Chapel and Dr. Joseph M'Benga appear as main cast members in Strange New Worlds, all played by different actors than The Original Series with the current actors playing Pike, Number One and Spock previously portraying the roles in Star Trek: Discovery
William Riker and Deanna Troi appear in the first season finale "No Small Parts," and Riker also appears in the season 2 episodes "Strange Energies" and "Kayshon, His Eyes Open"
A holographic statue of Miles O'Brien appears in the far future in the episode "Temporal Edict"
The Borg Queen appears as a hologram in the episode "I, Exctretus"
Sonya Gomez appears in the episode "First First Contact"
Morgan Bateson appears in a non-speaking role in the episode "Grounded"
An illusion of Leah Brahms appears in the episode "Mining the Mind's Mines"
Nick Lorcano appears in the episode "The Inner Fight" and he also appears with Wesley Crusher and Sito Jaxa in "Old Friends, New Planets."
An alternate reality version of Data appears in the episode "Fully Dilated."
Lily Sloane from an alternate universe appears in the episode "Fissure Quest" and has a non-speaking appearance in "The New Next Generation."
The Next Generation on Prodigy
Thadiun Okona appears in the episodes "Crossroads," Masquerade" and "Cracked Mirror"
A hologram of Beverly Crusher appears in the episode "Kobayashi" while the real Dr. Crusher appears in the episodes "Last Flight of the Protostar, Part II" and "Ouroboros, Part II"
Edward Jellico is a recurring character in both season 1 and season 2
Wesley Crusher joins the main cast starting with the season 2 episode "The Devourer of All Things, Part I". The Traveler also has a vocal cameo this episode.
Elim Garak and a holographic Julian Bashir from alternate universes appear in the episode "Fissure Quest" and also appear with no dialog in "The New Next Generation." An alternate version of Curzon Dax also appears in "Fissure Quest," voiced by Fred Tatasciore. (The Prime Universe version originally appeared in a non-speaking role played by Frank Owen Smith).
Deep Space Nine on Prodigy
Odo appears as a hologram in the episode "Kobayashi" via archival audio.
Voyager on The Next Generation series of films
The Mark I EMH "Doctor" appeared in the film Star Trek: First Contact. This EMH, while identical in name, appearance and mannerisms, was distinct from the Voyager character due to the nature of the EMH being a holographic computer program.
Seven of Nine has appeared five times in the first season episodes of Star Trek: Picard : "Absolute Candor", "Broken Pieces", "Et in Arcadia Ego: Part I", "Et in Arcadia Ego: Part II" and in "Stardust City Rag" she appears alongside Icheb in a final and brief cameo role. Icheb however is portrayed by different actors than those who had acted in the role on Star Trek: Voyager. Seven would go on to join the main cast for the second and third seasons.
Tuvok appears in two season 3 episodes: "Dominion", in which he was revealed to be an imposter, and "The Last Generation" which featured the real Tuvok.
Voyager on Lower Decks
Tuvok appears in a non-speaking role in the episode "Grounded"
Michael Sullivan, Doctor Chaotica and The Clown (originally portrayed by Fintan McKeown, Martin Rayner and Michael McKean, respectively) all appear in the episode "Twovix," with Chaotica played by James Sie, and Sullivan and The Clown voiced by uncredited actors.
Multiple versions of Harry Kim from alternate universes appear in the episode "Fissure Quest" and in non-speaking roles in "The New Next Generation."
Voyager on Prodigy
Kathryn Janeway is part of the main cast, appearing both as "Hologram Janeway" and the real Vice-Admiral Janeway.
Chakotay appears as a recurring character before joining the main cast in the season 2 episode "Last Flight of the Protostar, Part I"
An alternate reality version of T'Pol appears in the episode "Fissure Quest" and also in "The New Next Generation" in a non-speaking role.
Discovery on Short Treks
The characters of Tilly and Saru appear in the episodes "Runaway" and "The Brightest Star" respectively, with Phillipa Georgiou also appearing briefly in the latter episode
Younger versions of Michael Burnham and her father Mike Burnham appear in the animated episode "The Girl Who Made The Stars"
Short Treks on Discovery
Me Hani Ika Hali Ka Po from the Short Treks episode "Runaway" appears in both parts of the Discovery episode "Such Sweet Sorrow"
Siranna from the Short Treks episode "The Brightest Star" appears in the Discovery episodes "The Sound of Thunder", "Such Sweet Sorrow, Part 2" and through archival footage in "Lights and Shadows"
Picard on Prodigy
Jack Crusher, originally played by Ed Speleers, has a vocal cameo by Isabel Krebs
Lower Decks on Strange New Worlds
Brad Boimler and Beckett Mariner appear in both live-action and animation in the episode "Those Old Scientists". D'Vana Tendi, Sam Rutherford and Jack Ransom all appear in their animated forms.
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”[13]
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?"[13]
Brent Spiner (Data) plays Arik Soong in series 4, who is intended to be the great-grandfather of Noonien Soong, Data's creator.
The Next Generation on Picard
Brent Spiner (Data) plays Altan Inigo Soong in the first and third seasons and Adam Soong in the second season.
The Next Generation on Lower Decks
Stephen Root (Captain K'Vada) voices Lieutenant Gene Jakoboski in the episode "Starbase 80?!".
Deep Space Nine on The Original Series
Rene Auberjonois (Odo) also appears as Colonel West, a human assassin disguised as a Klingon intent on assassinating the Klingon Chancellor at the Khitomer Conference.
(Star Trek – Legion of Super-Heroes also reveals that DC's Vandal Savage and Flint, a mysterious immortal encountered by James T. Kirk and his crew, are actually parallel universe versions of the same person. While one version adopted the name Vandal Savage and dedicated himself to conquest, the other version adopted the name Flint and turned his life towards art and science.)
