Few television series have been as revolutionary as Star Trek. Launched in 1966, Star Trek survived two rejected pilot episodes, diminished budgets, and a second season cancelation to become one of the most profitable franchises ever. In addition to the original series, the franchise has included several movies and eleven spin-off series.

As successful as Star Trek has been, it isn’t perfect. Across the 884 episodes aired at the time of this writing, Trek has aired more than a few stinkers. Here are 25 of the worst, chosen from the original series and its many spin-offs. In the equality, a core Trek concept, every series has at least one representative, but no series has more than three entries on the list. And that makes sense because no matter how great Trek can be, some episodes should have never been beamed to our television sets.

1 – “Assignment: Earth” (The Original Series, Season Two, Episode Twenty-Six, 1968)

While the original series (TOS) remains one of the all-time great television series, even the most devoted Trekkies agree that the series’ third and final season is disappointing. But the quality dipped even in the second season, as demonstrated by the finale, “Assignment: Earth.” Intended to be a back-door pilot for a new show by Trek creator Gene Roddenberry, “Assignment: Earth” sends the Enterprise to 1968 Earth, where they meet agent Gary Seven, who would have been the hero of this proposed show. The gambit failed to launch a new series and forced Kirk and Spock to be supporting characters on their own show.

2 – “Spock’s Brain” (TOS, Season Three, Episode One, 1968)

A letter-writing campaign convinced CBS to reverse plans to cancel Star Trek after two seasons, but season three reminded them to be careful what they wished for. The problems begin with the season three premiere, “Spock’s Brain,” which involves an alien who, you guessed it, steals Spock’s brain. Trek often indulges its silly side but rarely belittles the characters or insults the viewers. “Spock’s Brain” does both. Wacky without making the most of the cast’s ability, “Spock’s Brain” was a fitting begin to the lackluster final season of TOS.

3 – “The Way to Eden” (TOS, Season Three, Episode Twenty, 1969)

Despite its 23rd Century setting, Star Trek has always been deeply interested in the present, often finding analogies to modern figures in the reaches of space. As clunky as these metaphors could sometimes be, they were never as annoying as the space-hippies in “The Way to Eden.” Under the leadership of quack academic Dr. Severin, the space hippies hijack the Enterprise to travel to the mystical planet Eden. Even ignoring the irritating kidnappers, the episode feels stuffy and preachy, surprisingly backward for the progressive series.

4 – “The Magicks of Megas-Tu” (The Animated Series, Episode Eight, 1973)

After the issues with season three of TOS, Star Trek: The Animated Series seemed like an unlikely miracle. So while the series did suffer from shoddy animation, even by the standards of tv cartoons of the day, it gave fans just a little more time with the Enterprise crew. But “The Magicks of Megas-Tu” pushes things too far. The cartoon medium lets writers indulge their sillier side with its story of Kirk and his crew encountering a figure from Earth mythology and religion, in this case, the Devil. For all its talk of reason over dogma, “The Magicks of Megas-Tu” comes off as sillier than the beliefs it tries to critique.

5 – “Code of Honor” (The Next Generation, Season One, Episode Four, 1987)

Star Trek: The Next Generation (TNG) famously had a rough beginning, as Gene Roddenberry struggled to bring Star Trek into the 80s and imposed arcane storytelling rules on writers. But “Code of Honor” is a bad episode, even by season one standards. There’s nothing inherently wrong with pitting the crew against a culture that differs from theirs, but writers drew from racial stereotypes when imagining the bad guys. Harmful even by 1960s standards, “Code of Honor” makes a mockery of the franchise’s principles of tolerance and acceptance.

6 – “The Child” (TNG, Season Two, Episode One, 1987)

After TOS became a cult hit in the 1970s, CBS planned a sequel series called Star Trek: Phase II, which brought back most of the original crew and paired them with new characters. The success of Star Wars convinced Paramount to make Star Trek: The Motion Picture in place of Phase II, but some of the canceled show’s scripts did get used in TNG. Unfortunately, many of these episodes felt outdated as standards shifted radically in the decade between writing and filming. That’s especially true of the TNG season two premiere, “The Child,” in which an alien entity impregnates Counsellor Troi. Beyond the pregnancy’s icky implications, “The Child” makes Troi an impassive fool in her own story.

7 – “Masks” (TNG, Season Seven, Episode Seventeen, 1994)

After a few bumpy seasons, TNG became a fantastic series filled with high-concept stories and beloved characters. But as the characters rose in prominence, the actors gained more control over the stories, and not always for the better. Case in point: “Masks,” in which the android Lieutenant Data encounters an alien entity with knowledge of a lost culture’s mythology. The alien possesses Data, driving him to act out stories from the culture’s past. The story allows actor Brent Spiner to show off his range, but it does not make for an engaging episode. By the time the credits roll, fans have had their fill of Data for a while.

8 – “Move Along Home” (Deep Space Nine, Season One, Episode Ten, 1993)

Darker and more politically complex than its predecessors, Star Trek: Deep Space Nine (DS9) pushed the Star Trek concept to new depths. Those richer themes make the season one misfire “Move Along Home” more embarrassing. When some of Star Trek’s dumbest-looking aliens visit the station, Sisko and his crew get stuck in a game, which subjects them to childish challenges. A ridiculous episode, “Move Along Home,” does a disservice to an otherwise compelling series.

9 – “Let He Who Is Without Sin…” (DS9, Season Five, Episode Seven, 1996)

It should have been a coup when Michael Dorn’s Klingon Starfleet office Worf came aboard Deep Space Nine, bringing a fan-favorite onto a new show. But the show too often turned Worf into an incompetent grouch, particularly in the season five episode “Let He Who is Without Sin…” Worf and his fiancée Jadzia Dax visit the pleasure planet Risa, but the free nature of the inhabitants offends the Klingons. Worf sabotages the planet's climate control system, and while he is chastised for the action, the show also forgives him for being an insecure boyfriend. Honestly, it is an episode without honor.

10 – “Profit and Lace” (DS9, Season Six, Episode Twenty-Three, 1998)

The Ferengi only lasted a few episodes as the primary enemy in TNG, as the greedy aliens were more annoying than dangerous. So it's a miracle that DS9 turned the reviled aliens into rich and beloved characters, largely thanks to performances by Armin Shimerman as Quark and Aron Eisenberg as Nog. That said, Ferengi-centric episodes tended to be among the show’s weakest, especially “Profit and Lace.” By making the male Quark dress like a woman, the show indulges in too many tired sitcom jokes from the 70s and 80s.

11 – “State of Flux” (Voyager, Season One, Episode Eleven, 1995)

The Ferengi made for terrible big bads on TNG, but they had nothing on the Kazon. Planned to be the primary enemy race of Star Trek: Voyager (VOY), the Kazon were a tribal people living in the Delta Quadrant where the USS Voyager was stranded. Inspired by a simplistic misunderstanding of California gangs and designed like Oompa-Loompas with pine cones glued to their heads, the Kazon rank among the worst aliens in the franchise. The first Kazon-focused episode, “State of Flux,” highlights all the problems with the aliens, which the series never fixes.

12 – “Elogium” (Voy, Season Two, Episode Four, 1995)

No character in Trek was set up to fail like Neelix, introduced as a guide and cook for the Voyager when it got lost in the Delta Quadrant. Eventually, Neelix became a likable crew member, largely thanks to Ethan Phillips’s warm performance. But for the first few seasons, writers made Neelix incredibly irritating and controlling, especially concerning his girlfriend Kes, an Ocampan who looked like an adult but was, in fact, two years old. Neelix’s toxic behavior climaxes in the season two episode “Elogium,” in which Kes enters an Ocampan mating state. It makes nasty implications about Kes, and Neelix comes off as clingy and gross, undercutting Phillips’s natural likability.

13 – “The Fight” (Voy, Season Five, Episode Fifteen, 1999)

As with Neelix, writers often undermined the Voyager’s commanding officer Chakotay. But his problems stemmed less from bad plots and more from the producers’ disastrous decision to hire a charlatan to advise on the characters’ Indigenous heritage. As a result, too many Chakotay-focused stories traded heavily in stereotypes about Native peoples, and actor Robert Beltran eventually grew tired of the role, as demonstrated by his lackluster performance. All these problems come together in “The Fight,” which brings back Ray Walston as kindly Starfleet Academy groundskeeper Boothby, but the stereotypical nonsense becomes tiresome.

14 – “Minefield” (Enterprise, Season Two, Episode Three, 2002)

If we’re being generous, we can see what the writers of Star Trek: Enterprise (ENT) planned for Tactical Officer Malcolm Reed. As a series about the beginnings of Starfleet, ENT featured characters still getting used to the idea of space travel, including Reed, the son of naval officers who struggled to adjust to Earth’s newest military branch. But too often, Reed came off as whiny and incompetent. Those grating qualities come to the fore in “Minefield,” in which Reed’s inability to disarm a mine leaves him trapped under rubbish. Reed spends the rest of the episode either mocking the command style of Captain Archer or complaining about his career, leaving us to wonder why they want to rescue him in the first place.

15 – “A Night in Sickbay” (Ent, Season Two, Episode Five, 2002)

In the eyes of most Trekkers, ENT has the weakest cast of any series. But no one dislikes Porthos, Captain Archer’s beagle best friend. So it would seem that the season two episode “A Night in Sickbay” would stand among the best, in which Archer spends the evening by the side of his sick dog. Despite the shots of the lovable canine, “A Night in Sickbay” focuses too much on Archer’s romantic life, leaning hard into the series’ tendency to leer at its female characters. The episode tries to undo any affection we might have for the dog-loving Pathos, rendering him an inappropriate leader.

16 – “These Are The Voyages” (Ent, Season Four, Episode Twenty-Two, 2005)

ENT tends to rank toward the bottom of the Star Trek shows. But even the angriest critic agrees that the show deserved better than its final episode, “These Are the Voyages.” Instead of giving the crew a proper sendoff or wrapping up the storyline from its markedly improved fourth season, “These Are the Voyages” focuses on Commander Riker from TNG. Riker uses his ship’s holographic computer to visit a simulation of the first Enterprise. Although the episode ends with a beloved character expressing admiration for a less-popular crew, the gesture feels condescending, only underscoring the show’s lesser status.

17 – “Into The Forest I Go” (Discovery, Season One, Episode Six, 2017)

One would think fans would be so happy to get a new Star Trek tv series in over a decade that they would forgive any oddity in Star Trek: Discovery (DISCO). But Discovery radically broke from tradition with deeply emotional stories, striking revisions of classic characters, and a darker overall tone. Many of those changes come together in “Into the Forest I Go,” which reveals the backstory of Klingon Voq, who serves on the USS Discovery disguised as the human Ash Tyler. Not only does the storyline include upsetting depictions of physical and psychological abuse, but it also features Klingon nudity, something no one wanted.

18 – “Project Daedalus” (Discovery)

Perhaps the most jarring aspect of DISCO is its abandonment of the ensemble model established by TNG and the TOS movies, focusing almost entirely on Michael Burnham and rarely on other crew members. Despite Sonequa Martin-Green's natural charisma, fans can’t help but wonder about the other people on the USS Discovery. “Project Daedalus” makes a mockery of those complaints by finally devoting attention to cyborg crew member Airiam only to kill her by the episode’s end. Rather than build the character, the backstory only justified the cloying climax, in which Ariam’s death provided more motivation for Michael Burnham.

19 – “Ephriam and DOT” (Short Treks, Season Two, Episode Four, 2019)

Star Trek: Short Treks (STK) has been one of the best parts of modern Trek, short one-off episodes that let us spend a bit more time with various characters around the franchise. The first season hit more than it missed, thanks to the horror-infused “Calypso” and hilarious Tribbles origin story “The Trouble With Edward.” At first glance, “Ephriam and DOT” continues the tradition, a slapstick-heavy tale of a robot and a tardigrade playfully battling each other on the Enterprise. Despite direction from Academy Award-winning composer Michael Giacchino, “Ephriam and DOT” makes a critical mistake by making a tardigrade the hero, given the abuse heaped upon such creatures in DISCO.

20 – “Children of Mars” (Stk, Season Two, Episode Six, 2020)

Short Treks sadly goes out with a whimper, thanks to the overwrought final episode “Children of Mars.” The episode follows two tween girls at a Federation school whose contentious relationship changes when both of their fathers die in an Android revolt. Set to Peter Gabriel’s rich cover of “Heroes” by David Bowie, the episode feels more like a public service message than a proper story, especially with its trite message. Making matters even worse, “Children of Mars” operates as a setup for the first season of Star Trek: Picard, which includes some of the franchise’s worst moments.

21 – “Stardust City Rag” (Picard, Season One, Episode Five, 2020)

Fans hoped the TNG sequel series Star Trek: Picard (PIC) would boost nostalgia, reuniting them with the Captain from their favorite show. But PIC intentionally swerved away from nostalgia, embracing a grimmer tone and presenting Picard as out of touch and unheroic. The opening to “Stardust City Rag” illustrates the problems with this approach, as it shows the brutal dismemberment and death of Icheb. A teenage former Borg who appeared in the second half of VOY, Icheb forged a mother/son bond with Seven of Nine. His death scene in PIC felt unnecessarily cruel, with cheap shock value to upset the audience.

22 – “Farewell” (Picard, Season Two, Episode Ten, 2022)

The best thing to be said about “Farewell” is that it ends Picard’s disastrous second season, which somehow combines the Borg, Q, alternate realities, and time travel. The season finale tries to tie up all those story threads, including the establishment of a new Borg Queen and the exit of several main cast members, while also giving an emotional goodbye to old TNG characters Q and Wesley Crusher. The result is a sloppy and unsatisfying story that makes Picard seem even more overwhelmed than usual. Fortunately, the closing of “Farewell” made way for PIC’s excellent third season, finally reuniting Picard with his former TNG crew.

23 – “All Those Who Wander” (Strange New Words, Season One, Episode Nine)

Unlike most Star Trek series, Strange New Worlds started strong and only improved. Set between DISCO and TOS, the show returns to the standalone stories of Trek’s heyday while giving characters and concepts a modern twist. The approach mainly works, but not in one specific case, as found in the season one episode “All Those Who Wonder.” The episode reintroduces the Gorn, a reptilian species first introduced as a sympathetic monster in a silly-looking mask in TOS. Strange New Worlds borrows heavily from the Alien franchise to make the Gorn dangerous predators, which robs the creatures of their original charm.

24 – “An Embarrassment of Dooplers” (Lower Decks, Season Two, Episode )

At its best, Lower Decks lovingly teases the wackier parts of Star Trek lore while also telling solid sci-fi stories. But Lower Decks’s rapid-fire sense of humor can sometimes become exhausting, devolving into a series of references instead of jokes or stories. Such is the case of the season two episode “An Embarrassment of Dopplers,” which finds the USS Cerritos on a disastrous diplomatic mission with an alien who duplicates when made uncomfortable. A funny idea, in theory, quickly becomes tiresome, despite the involvement of great character actor Richard Kind.

25 – “Lost and Found” (Prodigy, Season One, Episodes One and Two)

Honestly, it feels bad to include poor Star Trek: Prodigy on this list. Trek’s second animated series was a perfect way to introduce the series to children, thanks to its rag-tag crew of lovable aliens. But after one critically acclaimed season, Paramount canceled Prodigy and removed the show from its streaming service, making it very difficult to watch. Despite this bad luck and the fact that the show’s single season was largely delightful, Prodigy did begin with a whimper, thanks to the two-part premiere “Lost and Found.” The back-to-back episodes take too long to establish the show’s central premise, and Prodigy’s untimely demise only intensifies the sting of lost time.