As two of the most popular science fiction shows of all time, Star Trek and The X-Files share not only much of the same audience, but also many of the same actors. From the adventures of Captain Jean-Luc Picard (Patrick Stewart) and the USS Enterprise-D to those of Captain Benjamin Sisko (Avery Brooks) and space station Deep Space 9, Star Trek had a presence on television throughout all of the 1990s. With their episodic formats, both Star Trek and The X-Files had to bring in new actors each episode to portray the aliens (or monsters) of the week, so viewers of both shows likely saw many familiar faces.

The X-Files follows FBI Agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) as they investigate cases too strange for other agents to handle. While The X-Files may not have quite as much content as Star Trek, it did inspire eleven seasons of television, two feature-length films, and two spin-offs. Although The X-Files initially ended in 2002, the show returned in 2016 for two more seasons, and Black Panther director Ryan Coogler has been attached to a potential reboot since May of 2023. Here are the actors who jumped between Star Trek and The X-Files.

12 Callum Keith Rennie – Star Trek: Discovery

The X-files Season 1, Episode 15 (“Lazarus”); & Season 2, Episode 15 (“Fresh Bones”)

Callum Keith Rennie has not technically made his Star Trek debut yet, bu he will be joining the cast of Star Trek: Discovery season 5 as Captain Rayner, a no-nonsense Starfleet captain who gets the job done and excels during wartime. This will undoubtedly bring Rayner into conflct with Discovery‘s Captain Michael Burnham (Sonequa Martin-Green). Rennie appeared in two episodes of The X-Files; in season 1’s “Larazus,” he plays the unfortunate victim of a possessed FBI agent, and in season 2’s “Fresh Bones,” he appears as an unnamed cemetery groundskeeper.

11 Mark Sheppard – Star Trek: Voyager

The X-Files Season 1, Episode 12 (“Fire”)

A popular genre actor, Mark Sheppard is best known for portraying the demon Crowley on Supernatural, but one of his earliest roles was in a season 1 episode of The X-Files. In “Fire,” Sheppard plays a caretaker of a British estate who can conjure fire with his mind. In Star Trek: Voyager season 6, episode 19, “Child’s Play,” Sheppard portrays Leucon, the father of former Borg drone, Icheb (Manu Intiraymi). Although Captain Kathryn Janeway (Kate Mulgrew) believes Icheb’s reunion with his parents will be a happy one, she soon discovers that Icheb had been genetically engineered to be assimilated by the Borg and infect them.

10 Terry O’Quinn – Star Trek: The Next Generation

The X-Files Season 2, Episode 12 (“Aubrey”); Season 9, Episode 6 (“Trust No 1”); & The X-Files: Fight the Future.

Another well-known genre actor Terry O’Quinn may be best known for portraying John Locke on Lost, but he also appeared in a memorable role on TNG and on multiple episodes of The X-files. In Star Trek: The Next Generation season 7, episode 12, “The Pegasus,” O’Quinn played Admiral Eric Pressman, the former captain of the USS Pegasus and former commanding officer of Commander William Riker (Jonathan Frakes). O’Quinn appeared in two different episodes of The X-Files (“Aubrey” and “Trust No 1”), but his most significant X-Files role was as FBI agent Lt. Brian Tillman in the first X-Files movie, The X-Files: Fight the Future.

9 Tony Todd – Star Trek: Deep Space Nine, Star Trek: Voyager

The X-Files Season 2, Episode 4 (“Sleepless”)

Yet another iconic genre actor, Tony Todd may be most known for his horror-related roles, but he has popped up in several science fiction shows as well. Todd has appeared as three different Star Trek characters across three Star Trek shows. He portrayed the adult version of Jake Sisko in the celebrated Star Trek: Deep Space Nine episode, “The Visitor,” and was introduced as the Klingon Kurn, son of Mogh and brother of Lt. Commander Worf (Michael Dorn) in Star Trek: The Next Generation before returning as Kurn on DS9. Todd also appeared in Star Trek: Voyager season 4, episode 16, “Prey” as the leader of a group of Hirogen. Todd’s X-Files character is an ex-Marine who gained the power to craft illusions after a sleep deprivation experiment.

8 Susanna Thompson – Star Trek: Voyager, Star Trek: Deep Space Nine, & Star Trek: The Next Generation

The X-Files Season 1, Episode 9 (“Space”)

Susanna Thompson appeared as four different Star Trek characters, though her most significant role was as the Borg Queen in Star Trek: Voyager. Thompson portrayed Trill scientist Lenara Kahn in DS9 season 4, episode 5, “Rejoined,” which saw her share a kiss with Lt. Jadzia Dax (Terry Farrell). Because of the television and cultural landscape of the mid-1990s, the kiss between the two women made “Rejoined” a particularly controversial episode of Star Trek. Thompson also played minor characters in two episodes of TNG. In The X-Files, Thompson portrayed Michelle Generoo, a NASA communications commander who helps Agents Mulder and Scully uncover who is sabotaging NASA missions.

7 Hiro Kanagawa – Star Trek: Discovery

The X-Files Season 2, Episode 9 (“Firewalker”); Season 4, Episode 19 (“Synchrony”); & Season 10, Episode 1 (“My Struggle”)

A new addition to the Star Trek family, Hiro Kanagawa joined the cast of Star Trek: Discovery for the final few episodes of season 4 as Dr. Hirai. As an expert in astrolinguistics, xenophonology, and theoretical semiotics, Hirai worked with the crew of the USS Discovery to attempt to communicate with Unknown Species 10-C. Kanagawa has appeared in three different episodes of The X-Files, playing an ill-fated systems analyst in season 2’s “Firewalker” and equally ill-fated biology researcher Dr. Yonechi in season 4’s “Synchrony.” Kanagawa returned to The X-Files in 2016 to portray scientist Dr. Garner in the season 10 premiere, “My Struggle.”

6 Jennifer Hetrick – Star Trek: The Next Generation & Star Trek: Deep Space Nine

The X-Files Season 3, Episode 21 (“Avatar”)

Jennifer Hetrick is best known for playing Vash on two episodes of TNG and one of DS9. After Captain Picard met Vash while he was on holiday, the two developed a brief, but sweet romance. In her second appearance on TNG, Vash encountered Q (John de Lancie) and left with him to travel throughout time and space. In The X-Files, Hetrick portrayed Sharon Skinner, the wife of FBI Assistant Director Walter Skinner (Mitch Pileggi). Although Director Skinner continued to be a significant recurring character on The X-Files, the ultimate fate of Sharon Skinner after “Avatar” remains unknown.

5 Kurtwood Smith – Star Trek IV: The Undiscovered Country, Star Trek: Deep Space Nine, Star Trek: Voyager, & Star Trek: Lower Decks

The X-Files Season 3, Episode 14 (“Grotesque”)

Star Trek fans may recognize Kurtwood Smith first as the Federation President whose life was threatened in Star Trek VI: The Undiscovered Country, but he also made appearances in DS9 and Voyager. In DS9 season 5, episode 8, “Things Past,” Smith is unrecognizable as Thrax, a Cardassian who served as Chief of Security on Terok Nor before Constable Odo (René Auberjonois) took over the position. In Voyager, Smith portrays the main antagonist in the season 4 “Year of Hell” two-parter, Annorax. Smith appears as FBI Special Agent-turned-killer Bill Patterson in The X-Files. Smith also voiced Imperium Magistrate Clar in Lower Decks season 1, episode 8, “Veritas.”

4 Penny Johnson Jerald – Star Trek: Deep Space Nine, Star Trek: The Next Generation

The X-Files Season 8, Episode 12 (“Medusa”)

In addition to prominent roles on 24 and The Orville, Penny Johnson Jerald is best known to Star Trek fans for portraying Kasidy Yates on DS9. A freighter captain, Yates met Captain Benjamin Sisko (Avery Brooks) after Sisko’s son, Jake (Cirroc Lofton), introduced them. The two begin dating and eventually marry near the end of DS9’s run. The X-Files season 8 episode “Medusa” finds Agents Dana Scully and John Doggett (Robert Patrick) investigating a series of strange deaths in the tunnels beneath Boston. Jerald plays CDC pathogen specialist Dr. Hellura Lyle, who aids Scully and Doggett in their investigation.

3 Denise Crosby – Star Trek: The Next Generation

The X-Files Season 8, Episode 17 (“Empedocles”); & Season 8, Episode 20 (“Essence”)

Denise Crosby’s Lt. Tasha Yar began TNG as one of the show’s main characters, but she met a tragic death before the end of the first season. After Tasha’s death, Crosby would appear as various alternate incarnations of the character in later episodes of TNG. Yar also returned to TNG as Sela, Yar’s half-Romulan daughter from an alternate timeline. In The X-Files, Crosby appears briefly in two episodes as Dr. Mary Speake, the gynecologist attending to Dana Scully during the final months of her pregnancy.

2 Andrew Robinson – Star Trek: Deep Space Nine

The X-Files Season 6, Episode 16 (“Alpha”)

Andrew Robinson’s Elim Garak became one of the most interesting and beloved characters to come out of Star Trek: Deep Space Nine. The Cardassian spy-turned-tailor embodied the more morally grey aspects of DS9, setting him apart from most of Star Trek’s main characters. Although Garak made some questionable decisions, his charming personality and friendships with Odo and Dr. Julian Bashir (Alexander Siddig) made him a complicated and captivating character. Robinson appeared in The X-Files as cryptozoologist Dr. Ian Detweiler, who Mulder began to suspect may be able to shapeshift into a dangerous dog-like creature.

1 Anthony Rapp – Star Trek: Discovery

The X-Files Season 5, Episode 4 (“Detour”)

As the spore drive specialist on the USS Discovery, Anthony Rapp’s Commander Paul Stamets can connect to the mycelial network and propel the USS Discovery instantaneously across great distances. Stamets’ knowledge and passion for science have helped save Discovery on more than one occasion, and he and his husband, Dr. Hugh Culber (Wilson Cruz), have a wonderful and realistic relationship. Anthony Rapp played the small role of technician Jeff Glaser in The X-Files season 5 episode “Detour,” in which he used his infrared camera to help Agent Mulder. Anthony Rapp may be best known for originating the role of Mark Cohen in the Broadway musical Rent, but he’s also one of the few actors to play a main character in a Star Trek show and appear on The X-Files.