10 Best Star Trek Characters That Only Appeared In One Episode

"Star Trek" is famous for many things, but one of its best aspects is its incredible cast of characters. The show's diverse array of personalities, human and alien, gives everyone someone to identify with, root for, and even hate. Many of the best "Star Trek" characters also happen to be some of the most compelling in all of science fiction. But the brilliance of "Star Trek" characters isn't just limited to its main stars and series regulars. The franchise, which has been in existence since 1966, has a long track record of phenomenal guest characters. And believe it or not, some of the best are often found in just one episode.

From that classic original series of the 1960s to the current "Star Trek: Strange New Worlds," the franchise has a penchant for creating memorable and iconic characters for one episode alone. Guest actors, including some pretty big names, sign on for an episode, deliver masterful performances, and depart, never to be seen again. But that's the brilliance of these one-off characters: They don't need a whole series or a season — or even a two-part episode — to be as good as any regular cast member. Though it's hard to choose, given just how many the franchise has seen, we've found 10 of the best "Star Trek" guest stars who appeared in only one episode.

Some of the best single-episode guest stars on "Star Trek" have been fellow starship commanders. They give us a glimpse into the less-than-perfect captains out there who might not be quite as impressive or perfect as the likes of Kirk, Picard, Sisko, Janeway, or Pike. These heavily flawed heroes also provide a rich canvas to explore how our own commanding officers will respond to difficult crises, offering a contrast and counterpoint. The "Next Generation" Season 4 episode "The Wounded" is the perfect example, and the visiting Captain Maxwell demonstrates how an imperfect Starfleet officer can be far more interesting than the perfect ones.

Captain Maxwell — played by actor Bob Gunton, three years before he starred as the warden in "The Shawshank Redemption" — is the former commanding officer of Chief O'Brien (Colm Meaney) and a veteran of the Cardassian Wars. The Enterprise is sent to intercept him and his starship, the USS Phoenix, when Maxwell goes radio silent after destroying a Cardassian ship, apparently unprovoked. When Picard finds him, however, Maxwell insists that the Cardassians are arming for another war. He claims to be the only man who understands the threat, and is on a rogue mission to stop it. Picard is ordered to take Maxwell in, but the question is, could Maxwell be right?

More than just a complicated man, Maxwell is a soldier deeply affected by his past in the Cardassian Wars, but whose instincts could well be on the money. Yet his rogue mission raises moral questions, while his friendship with Chief O'Brien adds a new dimension to his character as well.

Despite being arguably the best "Star Trek" series, there aren't as many standout single-episode guest stars in "Star Trek: Deep Space Nine" as you might expect. That's largely owed to the show's more serialized nature, which meant it had far more recurring characters than other "Trek" shows. Nevertheless, "DS9" may boast the very finest one-shot character, or at least the most complex: Aamin Maritza, the Cardassian clerk from the acclaimed Season 1 episode "Duet."

Maritza is played by guest star Harris Yulin, the Emmy-nominated actor who today's audiences might recognize as Buddy Dieker from "Ozark." In "Deep Space Nine," his character arrives on the station and is immediately arrested when evidence suggests that he may be an infamous Cardassian war criminal named Gul Darhe'el. He is known as the Butcher of Gallitep for his slaughter of innocent Bajorans during the Cardassian occupation, but the man insists that he is simply a mere file clerk named Aamin Maritza. The rest of the episode is a cunning game of wits that forces everyone to question who he really is and what he really wants.

In the end, the man turns out to be who he claims he is, but he wants to be executed anyway: After years of guilt for participating in the occupation, he's looking to pay for his perceived crimes. As gripping as the episode is, it's Yulin as Martiza who makes it an all-time classic. His performance as both the innocent file clerk and the facade of an accused tyrant is nothing short of masterful, and helps explore the complexities of war.

"Star Trek: Voyager" may not lay claim to a lot of the best episodes in the franchise, but it also doesn't have many on the "worst" side either. There are plenty of underrated "Voyager" episodes, though, and one of the best among that bunch might be Season 2's "The Thaw." This "Twilight Zone"-like installment sees members of Captain Janeway's (Kate Mulgrew) crew trapped inside a virtual simulation on an alien world ruled by a psychotic computer program that takes the form of a circus clown.

Played by "This is Spinal Tap" and "Better Call Saul" star Michael McKean, the clown traps Harry (Garrett Wang) and B'Elanna (Roxann Dawson) inside the simulation, which is designed to keep the survivors of an ecological disaster alive on an alien world. But his programming, designed to keep their brains active and "entertained," has instead become a monster that feeds on their fear and seems to take a perverse pleasure in torturing them.

Devilishly sinister, but with a calm and calculating streak, the Clown controls his reality and isn't fooled by Janeway and her attempts to trick him into releasing her poeple from his grasp. While it might be easy to make comparisons to "It" villain Pennywise, the Clown in "The Thaw" is terrifying for a very different reason: Because he's smart, controlling, and manipulative. Plus he can tap into a person's mind, giving him access to everything about them — even things they might not know about themselves. 

The Season 5 "Star Trek: The Next Generation" episode "Darmok" might be among the most widely known entries of that series. It's garnered critical acclaim and universal praise from fans for its lesson on communication and understanding your enemy. Like the "Original Series" episode "Arena," the story sees the Enterprise's commanding officer abducted alongside a rival starship captain, Dathon (Paul Winfield), and forced to fight to the death on a barren alien world. This time, however, the two captains must fight side by side against a monstrous alien beast.

The rival captain Dathon is played by Paul Winfield, who impresses in his sole guest appearance because he only speaks in an alien tongue. In fact, his language, as Captain Picard (Patrick Stewart) learns, utilizes metaphor to communicate ideas, which has left Dathon's people isolated because nobody has ever been able to decipher it. This strange language forces Winfield to act not with words, but with gestures and tone alone. Yet, despite the viewer being barely able to understand a word that he's saying, Winfield is able to turn Dathon from a mysterious alien enemy into a heroic, tragic figure who is willing to give his life for the sake of communication: He puts himself in this situation because what he wants, more than anything, is for someone to understand him.

An iconic episode with its own memorable catchphrase ("Darmok and Jalad at Tanagra"), the episode has even been used in college courses as a demonstration of understanding different kinds of languages. But much of the story is propped up by Winfield's striking performance as Dathon.

Though the Klingons and the Borg often get all the attention, it's the Romulans that might actually be the biggest villains on "Star Trek: The Next Generation." The ongoing conflict between the Federation and the Romulans was the backbone of more than a dozen key episodes, and while they made their series debut in the Season 1 finale, it was the Season 3 episode "The Defector" that really kicked the story into high gear. And guest star James Sloyan, who plays a defecting Romulan officer named Jarok, is the biggest reason why it all works so well.

"The Defector" sees Jarok fleeing his own empire and taking refuge aboard the Enterprise. He initially presents himself as a mere low-ranking logistics officer, and claims to have inside information on a planned Romulan attack on the Federation. But as Captain Picard questions him, the more his story starts to fall apart. Yet there is evidence that he may be telling the truth — evidence that is called into question when they discover he is really Admiral Jarok, a notorious figure who is believed to be responsible for a massacre earlier in his military career. 

Jarok insists to Picard that he is defecting to save his people from another bloody conflict. But his desperate cry for help — wishing to spare his children the scars of war — sadly seems to fall on deaf ears, as Jarok claims to want to change his warmongering ways. He's a complicated figure with a dark past, but one we still somehow find ourselves having sympathy for.

"Star Trek" has a long history of evil admirals, affectionately known to fans as "badmirals." These high-ranking Starfleet officers usually cause problems for our heroes, often by giving orders that cross ethical lines. This can make for some of the most powerful episodes of "Star Trek," but their success always hinges on how good the visiting admiral is as a character. And one of the best we've ever seen is Admiral Satie (Jean Simmons), who comes aboard the Enterprise to uncover a conspiracy in the "Next Generation" Season 4 episode "The Drumhead."

Admiral Norah Satie, according to Picard, is a highly accomplished retired officer and investigator who has served the Federation with distinction for decades. She's also the daughter of legendary Federation diplomat Aaron Satie. She comes to the Enterprise in search of answers when a Klingon saboteur is found aboard the ship, and is believed to have an accomplice among the crew. But in her ruthless search for a suspect, Satie sparks a witch hunt aboard the ship that drags in even Captain Picard, who she brazenly accuses of treason.

"The Drumhead" is a powerful episode about the dangers of fear-based investigations and how easily democracy and freedom can be subverted in a search to find an enemy. It's also one of the best courtroom episodes in the franchise, and guest star Jean Simmons delivers a strong performance as Satie, a woman so obsessed with finding the truth that she is blinded by her own paranoia.

Evil admirals aren't the only Starfleet officers to plague the various "Star Trek" crews. In one of the best episodes of the original "Star Trek" series, in fact, it was a Starfleet Commodore who broke bad, menacing Captain Kirk and the Enterprise in the Season 2 episode "The Doomsday Machine." The episode involves the discovery of an ancient, devastating weapon that can consume entire planets, which it uses for fuel — not unlike a certain "Fantastic Four" world-devourer. When Kirk (William Shatner) is stranded on Commodore Matt Decker's (William Windom) derelict starship, it falls to the maniacal officer to stop this interstellar threat.

Decker's ship, the USS Constellation, has an ill-fated run-in with the doomsday machine, and when the Enterprise comes to investigate, Decker — the only survivor — is sent to the Enterprise. But when the planet-eater returns and Kirk is trapped aboard the Constellation, Decker takes command of the Enterprise for a mission of revenge. The only problem is that the attack on his ship that killed his entire crew has left Decker mad, and he's willing to sacrifice anything and anyone for his personal vendetta against the world-destroying monstrosity.

Many fans out there are unhappy with the more recent crop of "Star Trek" series that began with "Star Trek: Discovery." While only time will tell if they prove as memorable as shows like "The Next Generation" or "Deep Space Nine," the 2022 prequel series "Star Trek: Strange New Worlds" has demonstrated its worth with a dramatic new look at the voyages of the original starship Enterprise before Captain Kirk. And the episode "The Serene Squall" added a new guest star to the pantheon of one-off greats: Captain Angel, played by Jesse James Keitel.

Though we wouldn't normally call out the fact that Keitel is a nonbinary trans actor, their gender identity is important to this Season 1 episode in a meta way. Angel arrives claiming to need the Enterprise's help in stopping a series of raids by cosmic pirates, but in a stunning twist, they are revealed to be the leader of those same rogue agents. But under the guise of friendship, Angel helps Spock (Ethan Peck) to understand and come to terms with his half-Vulcan, half-human nature, stressing that he need not choose between one or the other: He can be something else entirely that isn't so binary. 

But Angel isn't a one-note character; they're also a brilliant adversary for the Enterprise, the kind of villain whose scheme you don't see coming until it's too late. And their story also ties into deep "Star Trek" lore, as their ultimate goal brings back Spock's half-brother Sybok, one of the franchise's most underrated villains.

"Star Trek" has long been known for its big-name guest stars who pop in for a single episode. In fact, there are many actors who appeared in "Star Trek" and went on to huge careers, and one of the earliest is Joan Collins, who audiences knew later for her long-running role in the 1980s prime time soap opera "Dynasty." Decades earlier, she played a major role in one of the best episodes of the original "Star Trek" series: the 1967 Season 1 classic, "The City on the Edge of Forever."

Penned by acclaimed author Harlan Ellison, "The City on the Edge of Forever" sees Kirk and Spock (Leonard Nimoy) travel back in time to the 1930s, where Dr. McCoy (DeForest Kelley) has inadvertently altered history by mistake. Spock discovers that the source of the change to the timeline is Edith Keeler (Joan Collins), a charity worker who must die if they are to restore history to its proper course. But Kirk and Edith fall in love, forcing Kirk to let the woman he loves be killed to save the future.

Keeler is a noble young woman who wants to help the impoverished, and Collins plays her as a compassionate and caring soul — whose own demise will stop the deaths of countless millions to come. 

"Star Trek" is famous for its stories of morality and social allegory that examine today's problems through the lens of tomorrow. In fact, there are even "Star Trek" episodes that are still debated decades later. Firmly falling in that category is the "Star Trek: Voyager" Season 2 episode "Tuvix," which forces Captain Janeway into an ethical dilemma when she is left to decide who lives and who dies. It's all thanks to Tuvix (Tom Wright), a new character who is created in a transporter accident that mixes the DNA of Tuvok (Tim Russ) and Neelix (Ethan Phillips).

Tuvok and Neelix cease to exist and are merged into one new being, who names himself Tuvix. He has both Tuvok and Neelix's memories and a mix of their personalities, but he is distinctly his own, unique person. The Doctor (Robert Picardo) helps devise a way to send Tuvix back through the transporter and bring Tuvok and Neelix back to life, but the procedure would effectively kill Tuvix in the process — and he doesn't want to go through with it.

Among the show's best episodes, "Tuvix" is elevated by guest star Tom Wright, who plays the title character to perfection, with characteristics of both Neelix and Tuvok, while still being his own person. He also delivers a punch to the gut in the episode's final moments, with his pleading cries for life that will leave you with tears in your eyes — no matter how you feel about the moral choice.