In 1966, Star Trek, better known as Star Trek: The Original Series or TOS, introduced audiences to a vast universe occupied by unique and memorable characters, most of whom are aliens. As a result, many actors have guest-starred on the show, either as recurring characters or as one-time guest stars.
Some of these actors, however, have had the opportunity to appear in the sequel and spin-off Star Trek shows, everything from TNG to DS9, to Discovery. A handful of these actors reprised their original TOS roles while others took on new and exciting characters.
17 Stanley Adams voiced Cyrano Jones in the animated series after playing him in TOS
In the fan-favorite episode "The Trouble with Tribbles," Adams plays Cyrano Jones, the intergalactic tradesman who was responsible for the tribble infestation on Deep Space Station K-7. He was ultimately sentenced to prison but manages to escape and make a reappearance in the animated series episode "More Tribbles, More Troubles."
In the episode, he once again runs into a problem with the tribbles and comes into the possession of a Klingon predator tribble called a glommer. Stanley Adams was one of the only non-regular cast members to have been in both TOS and the animated series.
16 Malachi Throne voiced the Keeper & played Commodore José I. Mendez in the original series; Throne would later play Pardek, a Romulan politician, in TNG
Though the Keeper was physically played by Meg Wyllie, Throne voiced the character. The Keeper was a Talosian, a race of telepathic and sentient aliens from the planet Talos IV, who tried to convince Captain Pike, captain of the Enterprise prior to Kirk, to stay and live out the rest of his life with Vina on Talos IV. The Keeper appears in "The Cage," "The Menagerie, Part I," and "The Menagerie, Part II." In "The Menagerie, Part I" and "Menagerie, Part II," Throne also played Commodore José I. Mendez, the commander of Starbase 11 where Captain Pike was hospitalized after his exposure to delta radiation.
In "Unification I" and "Unification II" from TNG, Throne appeared as Pardek, a Romulan politician who befriends Spock. He appeared to be an ally at first but his ulterior motives were soon revealed and thwarted by Data and Picard.
15 Jack Donner portrayed Tal, a Romulan Sub-Commander, in TOS & a Vulcan priest in Enterprise
Jack Donner is one of the few actors to have appeared in both the original series and in Enterprise. In "The Enterprise Incident," Donner is the Romulan Sub-Commander Tal. Tal assumes command of the ship after his captain is apprehended while trying to seduce Spock.
Donner returns to the Star Trek franchise in Enterprise, playing a Vulcan priest. He appeared on two episodes, "Home," where he marries T'Pol and Koss, and "Kir'Shara," where he removes Surak's mind essence from Captain Archer.
14 Iona Morris made a minor appearance in the original series as an Onlies & then as Umali, an alien bartender, in Voyager
Iona Morris played a girl who was part of the Onlies, a group of orphaned children from a planet near identical to Earth in "Miri." Due to a life-prolonging project gone wrong, the adults on the planet have died off, leaving the children to fend against the virus and infected adults for themselves.
In "Workforce" from Voyager, Morris returned as Umali, an alien bar owner who worked on the planet Quarra. She hires an amnesiac Tom Paris. After Tom tries to increase his workplace reputation by giving away free drinks, Umali calls him out on his act.
13 Brian Tochi played Ray Tsing Tao in the original series & Ensign Lin on TNG
Tochi was 9 when he appeared as Ray Tsing Tao in the episode "And the Children Shall Lead." In the episode, Tao is one of the surviving children from the planet Triacus. Tao and the rest of the children in his party are under the influence of a mysterious entity who plans on stealing the Enterprise and enslaving more children elsewhere in the galaxy.
Tochi reappears, 23 years after his role as Tao, as Ensign Lin in TNG. He is an ensign on the Enterprise-D, captained by Picard, who takes over the helm from Sariel Rager when she forgets how to operate the console after the starship entered the Tyken's Rift in "Night Terrors."
12 William Schallert was Nilz Baris in TOS & a Bajoran musician named Varani in DS9
In the TOS episode "The Trouble with Tribbles," Schallert asserts the role of Niltz Baris, the Undersecretary who oversaw the transfer of quadrotriticale grain from Earth to Sherman's Planet from Deep Space Station K-7. He soon becomes a pester to Kirk and their contention, though lighthearted, is a subplot for the episode.
Schallert returns in DS9 as the Bajoran musician Varani in the episode "Sanctuary." Varani attempts to restore part of the Bajoran culture, partially destroyed by the Cardassian occupation, by asking Major Kira to ask the Provisional Government to consider rebuilding the Jalanda Forum, a public event center, on Bajor.
11 John Colicos reprised his role as the Klingon Kor in DS9
Most fans might not be familiar with the name Colicos but many are familiar with his character from "Errand of Mercy." Kor was one of Captain Kirk's more formidable foes, commanding the IKS Klothos. He is shown to be a cunning and deviant commander during his time on TOS.
Colicos reprised his role as Kor in Ds9 in the episodes "Blood Oath," "The Sword of Kahless," and "Once More Unto the Breach." In DS9, Kor, now looking like a more traditional Klingon, finds himself at odds with the current Klingon Empire, particularly with Chancellor Gowron, and is struggling to keep his relevancy and fame within the empire. Because of this, his story becomes intertwined with Worf's.
10 Michael Pataki portrayed the Klingon Korax in TOS & Karnas in TNG
Michael Pataki played the Klingon Korax in the TOS episode titled "The Trouble with Tribbles." In the episode, he famously gets into a scurry with Scotty and Chekov, and subsequently Miles O'Brien and Julian Bashir, after insulting the Enterprise and Captain Kirk.
Michael Pataki later returned to Star Trek and portrayed Karnas in the TNG episode "Too Short a Season." Karnas was the governor of a planet called Mordan IV. While leader, he takes a Starfleet ambassador and his crew hostage in order to exact revenge on Starfleet Admiral Mark Jameson, who had a significant role in instigating a civil war on the planet years earlier.
9 Charles Napier played Adam in TOS & Lt. General Dennings in DS9
In the TOS episode "The Way to Eden," Napier plays Adam, a hippy, musician, naturalist, and disciple of Dr. Sevrin, a cult leader. Adam and Dr. Sevrin attempt to find Eden, commandeering various shuttles and starships along the way.
Napier also played Lt. General Denning in the Ds9 episode "Little Green Men." In an attempt to transport Nog to the Starfleet Academy on Earth, Quark, Nog, and Rom are sent back in time to 1947 Roswell, New Mexico. There they meet Lt. General Denning, the person overseeing the investigation into the alien incursion.
8 Charlie Brill was Arne Darvin in both TOS & Deep Space Nine
In "The Trouble with Tribbles," Charlie Brill played Arne Darvin, a Klingon spy who was physically altered to appear human. He poisons a shipment of quadrotriticale grain and attempts to send it to Sherman's Planet. Kirk manages to foil his plot using a tribble.
Brill reprises his role as Darvin in the DS9 episode "Trials and Tribble-ations." In this episode, Darvin travels back in time, along with the rest of the DS9 crew, using the Orb of Time to take revenge on Kirk, thereby altering the original timeline.
7 William Campbell portrayed the alien Trelane in the original series & the Klingon Warrior Koloth in the original series & in DS9
Trelane was an alien from the planet Gothos in the TOS episode "The Squire of Gothos." Fans often compare him to the character Q, who would later be introduced in TNG, due to his abilities and beliefs regarding humans. He toyed with Kirk and often meddled in the lives of the crew on the Enterprise.
Koloth was the captain of the IKS Gr'oth in "The Trouble with Tribbles." While taking shore leave at the Federation Deep Space Station K-7, some of his crew, including his first mate Korax, starts a physical altercation with Scotty and Chekov. Koloth then confronts Kirk about the brawl and demands he issue an apology. In the DS9 episode "Blood Oath," Koloth, once again portrayed by Campbell, along with Kang, Kor, and Jadzia Dax, seek to find The Albino, a criminal who infected and killed Koloth's firstborn son with a virus.
6 Michael Ansara played the Klingon Kang in TOS, DS9, & in Voyager. He also played Jeyal, the Tavnian ex-husband of Lwaxana Troi, in DS9
In the TOS episode, "Day of the Dove," the crew of the enterprise responds to a distress call from the planet Beta XII-A. While exploring the planet, a Klingon ship arrives, damaged, under the command of Kang. Kang accuses Kirk of attacking his ship and proceeds to commandeer the Enterprise. Fast forward to the DS9 era, in "Blood Oath," Ansara reprised his role as Kang, who is now an ambassador and close friends with Curzon Dax, the godfather of his firstborn son. Like Koloth and Kor, he seeks the Albino for murdering his firstborn son with a virus.
Ansara once again played Kang in the Voyager episode "Flashback," where Kang congratulates Sulu for his promotion to captaincy. Ansara also portrayed the alien Jeyal, the now ex-husband of Lwaxana Troi, in the DS9 episode "The Muse." Jeyal demands that their expectant son be raised only by men, as according to Tavnian standards, to which Troi responds by running away to Deep Space 9.
5 Roger C. Carmel played Harry Mudd in TOS & later voiced him in Star Trek: The Animated Series
Carmel played Harcourt Fenton "Harry" Mudd, professional conman and smuggler, in "Mudd's Women" and "I, Mudd." He first attempts to marry off three women under the effects of an illegal Venus drug, which enhances their attractiveness, to a group of lithium miners. Mudd then returns from jail and becomes trapped on a planet full of androids looking to study humanity.
Carmel reprised his role as Mudd in the episode "Mudd's Passion" from the animated series. In the episode, Mudd apparently escapes the android planet and attempts to make a profit from a concocted love potion. His plans quickly go awry.
4 Joseph Ruskin appeared on TOS, DS9, Voyager, & Enterprise as various characters
Ruskin is one of a few actors to have appeared on multiple Star Trek series. He appeared in "The Gamesters of Triskelion" as Galt, the master thrall on TOS. In Ds9, he portrayed the Klingon Tumek, advisor to Grilka, ex-wife of Quark, in "The House of Quark" and "Looking for par'Mach in All the Wrong Places." He also played a Cardassian informant in "Improbable Cause."
In the Voyager episode "Gravity," he was a Vulcan master who taught Tuvok to better control his emotions. He also played a Suliban doctor in the Enterprise episode "Broken Bow." Lastly, Ruskin appeared in Star Trek: Insurrection as a Son'a officer aboard Ru'afo's ship.
3 Clint Howard was on TOS, DS9, Enterprise, & Discovery
As of now, Howard is the only actor to have appeared in the original series and in the latest series, Discovery. There was more than a 50-year gap between these two appearances. Howard was first the physical actor for Balok, an alien from the First Federation who captained the Fesarius, in "The Corbomite Maneuver" from TOS. In the Ds9 episode "Past Tense, Part II," he was Grady, a homeless man who believed in aliens; he later meets and interacts with Jadzia.
In "Acquisition" from Enterprise, he was a Ferengi pirate named Muk who boards and attempts to loot the Enterprise. More recently, in "Will You Take My Hand?" from Discovery, he portrayed a creepy Orion man from Qo'nos who had a rather strange interaction with Sylvia Tilly.
2 Phil Morris played five different characters across three series (TOS, DS9, Voyager) & a movie
Similar to Iona Morris, Phil Morris' first role was in the TOS episode "Miri" as one of the Onlies, though he was not credited. He would later return to play Thopok in the DS9 episode "Looking for par'Mach in All the Wrong Places" and a Jem'Hadar soldier named Remata'Klan in "Rocks and Shoals." Morris returned to Star Trek in the Voyager episode "One Small Step" as astronaut Lt. John Kelly.
And lastly, in Star Trek III: The Search for Spock, he was Foster, a Starfleet cadet who asked Kirk if there would be a hero's welcome when the Enterprise returned to Earth.
1 Mark Lenard reprised his role as Sarek, Spock's father, in TNG, the animated series, & in three of the Star Trek films
Although he played various roles in TOS, his most notable was as Sarek, Spock's Vulcan father. Sarek first appeared in "Journey to Babel" along with his human wife Amanda, Spock's mother. Lenard appeared again as Sarek in "Yesteryear," from the animated series, Star Trek III: The Search for Spock, Star Trek IV: The Voyage Home, and in Star Trek VI: The Undiscovered Country.
Lenard returned once again as Sarek in the TNG episodes "Sarek" and "Unification I." In TNG, Sarek is diagnosed with Bendii Syndrome and eventually dies from the condition.