10 'Star Trek: The Original Series' Episodes Everyone Should Watch at Least Once
Born with Autism (formerly classified as Asperger syndrome), Tyler B. Searle has been obsessed with storytelling since he was old enough to speak. He gravitated towards fairy tales, mythology, the fantasy genre, and animated movies and shows aimed at family audiences. When not writing, Tyler enjoys watching more cartoons and reading fantasy books in his home in Ontario, Canada.
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There are few franchises that have had the same impact on popular culture as Star Trek. First appearing in 1967 with what is retroactively referred to as Star Trek: The Original Series, the series has enthralled audiences for almost 60 years with its exploration of high concepts within the science-fiction genre, touching on deep philosophical quandaries about human nature, our place in the wider universe, and commentary on contemporary politics, just to name a few. It has gone on to shape countless sci-fi stories since, and in some ways even predicted future technologies.
While the original series is in some ways dated due to its effects and the at-times hammy acting, it is still chock-full of episodes with stellar writing and creative ideas, especially for the time it was released. Even if you're not a huge fan of Star Trek, some episodes are still worth watching at least once.
10 "The Trouble with Tribbles" (Season 2, Episode 15)
The Enterprise is summoned to Deep Space Station K7 to transport a shipment of hybrid grain to Sherman's Planet in the hopes that the grain can grow there, lest the planet instead be given over to the Klingon Empire. Speaking of Klingons, one of their ships arrives at the station, further complicating things for Captain Kirk (William Shatner). As if all of that wasn't bad enough, Lieutenant Uhura (Nichelle Nichols) purchases a small fuzz ball called a Tribble, a species that seems to both hate Klingons and reproduce at an alarming rate.
"The Trouble with Tribbles" is an episode that focuses less on high-style concepts and more on just being an entertaining hour of television. It's full of hilarious moments, from a bar fight between the Enterprise and Klingon crews, and Kirk's mounting frustration, especially because he is repeatedly bombarded by tribbles. Speaking of the little fuzzballs, they are such a simple but effective idea for a creature, and their popularity saw them return numerous times in future Star Trek shows.
9 "The Corbomite Maneuver" (Season 1, Episode 10)
While exploring an unknown region of space, a mysterious cube begins following the Enterprise and emitting harmful radiation. When it refuses to disengage, Kirk orders its destruction. Shortly after, a truly gigantic starship arrives, captained by Commander Balok (Clint Howard and Ted Cassidy), who declares that the Enterprise destroyed a border marker belonging to the "First Federation," and that he will destroy the Enterprise in turn.
"The Corbomite Maneuver" is perhaps the episode where the original series finally found its footing. It contains many of the franchise's best aspects: a brilliant sense of discovery through delving into the unknown, strong character interactions, solid worldbuilding, and clever twists that leave you eager to see what will come next. The titual maneuver is also one of Captain Kirk's best moments, demonstrating his cunning brilliance when under pressure, and how capable he is of selling a bluff.
8 "The Enemy Within" (Season 1, Episode 5)
While beaming an injured geologist back aboard the Enterprise, an unknown ore dust on his clothing results in a transporter malfunction. Captain Kirk is split into two when beamed aboard: his "good half" who is dutiful but passive, and his "evil half," who is self-indulgent and aggressive. Spock (Leonard Nimoy) shuts down the transporter until they can find a way to re-unite the two Kirks, which leaves the rest of the away team stranded as the planet's temperatures plummet to below freezing.
"The Enemy Within" takes a simple idea of an evil alter ego and expands it into an enthralling episode of television. It explores the dual nature of humanity through the two Kirks, forgoing a simple good vs evil approach for a more complex one that showcases how traits we deem positive and negative can so easily be flipped if we lack the necessary drive and restraint to use them properly. As for the two Kirks, Shatner delivers a truly legendary dual performance that fills the episode with deep moments of retrospection and aggressive outbursts that let him chew all of the scenery.
7 "Space Seed" (Season 1, Episode 22)
The Enterprise happens upon an ancient Earth ship that has living humans in suspended animation. They tow the ship and wake up the group's leader, Khan Noonien Singh (Ricardo Montalbán), a charismatic individual possessing incredible physical and mental abilities. Unfortunately, it turns out Khan and his crew are super soldiers from Earth's Eugenic Wars, and he begins manipulating historian Lieutenant Marla McGivers (Madlyn Rhu) into helping him take control of the ship.
"Space Seed" introduces Khan, one of the series' most iconic villains, who would return for the most celebrated film in the franchise, Star Trek II: The Wrath of Khan. The reason for his success can mainly be attributed to Montalbán's performance: he controls every scene he is in, perfectly selling Khan as a deadly opponent for the Enterprise who is always taking stock of the situation and planning how best to make use of this new information. Beyond Khan himself, the episode is also a stellar example of how to write a bottle episode—an episode of television that minimizes cost by restricting itself to a single location and small cast.
6 "Mirror, Mirror" (Season 2, Episode 4)
While beaming up after a failed diplomatic mission, Kirk, Scotty (James Doohan), Dr. McCoy (DeForest Kelley), and Uhura are caught in a storm. When they arrive on the Enterprise, they discover that their uniforms have changed, Spock has a beard, and the ship and its crew serve a militaristic empire rather than an optimistic federation. It turns out they've been sent to a parallel universe, and until they can find a way back, they must play the role of their alternate selves on a ship where everyone is waiting for the chance to kill the person above them in the chain of command.
"Mirror, Mirror" is the first episode to feature the Mirror Dimension, and has a lot of fun with the premise. It's fascinating and terrifying to see the crew of the Enterprise as self-serving warmongers, and how deadly the Federation could be if it ever veered away from its commitment to exploration and cooperation among the stars. Mirror Spock is the highlight of the episode: not only does the addition of the beard add so much to the character, but the logical and analytical mind that makes the original Spock such an effective Science Officer now turns him into a cunning individual who will do whatever it takes to maintain his position and security.
Collider Exclusive · Sci-Fi Survival Quiz Which Sci-Fi World Would You Survive? The Matrix · Mad Max · Blade Runner · Dune · Star Wars
Five universes. Five completely different ways the future went wrong — or sideways, or up in flames. Only one of them is the world your instincts were built for. Eight questions will figure out which dystopia, galaxy, or desert wasteland you'd actually make it out of alive.
💊The Matrix
🔥Mad Max
🌧️Blade Runner
🏜️Dune
🚀Star Wars
01
You sense something is deeply wrong with the world around you. What do you do? The first instinct is often the truest one.
02
In a world of scarcity, what resource do you guard most fiercely? What we protect reveals what we believe survival actually requires.
03
What kind of threat keeps you up at night? Fear is useful data — if you're honest about what you're actually afraid of.
04
How do you deal with authority you don't trust? Every dystopia has a power structure. Your approach to it determines everything.
05
Which environment could you actually endure long-term? Survival isn't just tactical — it's physical, psychological, and very much about where you are.
06
Who do you want in your corner when things fall apart? The company you keep is the clearest signal of who you actually are.
07
Where do you draw the line — if you draw one at all? Every survivor eventually faces a moment that tests what they're actually made of.
08
What would actually make survival worth it? Staying alive is one thing. Having a reason to is another.
Your Fate Has Been Calculated You'd Survive In…
Your answers point to the world your instincts were built for. This is the universe your temperament, your survival instincts, and your particular brand of stubbornness were made for.
The Matrix
You took the red pill a long time ago — probably before anyone offered it to you. You're a systems thinker who can't help but notice the seams in things.
- You're drawn to understanding how the system works before figuring out how to break it.
- You'd find the Resistance, or it would find you — your instinct for spotting constructed realities is the machines' worst nightmare.
- You function best when you have access to information and the freedom to act on it.
- The Matrix built an airtight prison. You'd be the one probing the walls for the door.
Mad Max
The wasteland doesn't reward the clever or the well-connected — it rewards those who are hard to kill and harder to break. That's you.
- You don't need comfort, community, or a cause larger than the next horizon.
- You need a vehicle, a clear threat, and enough fuel to outrun it — and you're good at all three.
- You are unsentimental enough to survive that world, and decent enough — just barely — to be something more than another raider.
- In the wasteland, that distinction is everything.
Blade Runner
You'd survive here because you know how to exist in moral grey areas without losing yourself completely.
- You read people accurately, keep your circle small, and ask the questions others prefer not to answer.
- In a city where humanity is a legal designation rather than a feeling, you hold onto something that keeps you functional.
- You're not a hero. But you're not lost, either.
- In Blade Runner's world, that distinction is everything.
Dune
Arrakis is the most hostile environment in the known universe — and you are precisely the kind of person it rewards.
- Patience, discipline, and political awareness are your core strengths — and on Arrakis, they're survival tools.
- You understand that the long game matters more than any single victory.
- Others come to Dune and are consumed by it. You'd learn its logic and earn its respect.
- In time, you wouldn't just survive Arrakis — you'd begin to reshape it.
Star Wars
The galaxy far, far away is vast, loud, and in a constant state of violent political upheaval — and you wouldn't have it any other way.
- You find meaning in being part of something larger than yourself — a cause, a crew, a rebellion.
- You'd gravitate toward the Rebellion, or the fringes, or whatever pocket of the galaxy still believes the Empire's grip can be broken.
- You fight — not because you have to, but because standing aside isn't something you're capable of.
- In Star Wars, that willingness is what makes all the difference.
5 "The Doomsday Machine"
While investigating several destroyed planets, the Enterprise finds its sister ship, the USS Constellation, badly damaged and manned by only one member of the crew: Commodore Matt Decker (William Windom). He explains that the ship was attacked by a gigantic alien craft that killed his crew after they were beamed down to one of the now destroyed planets, and Kirk orders the Constellation towed and stays aboard to oversee repairs to her engines. However, the alien device soon returns, and Decker assumes command of the Enterprise in order to destroy it before the weapon can enter Federation space.
"The Doomsday Machine" is a fantastic example of Star Trek's ability to tap into cosmic horror. In this case, the titular machine represents an uncontrollable weapon that exists long after its creators are gone, continuing its functions and leaving only a trail of destruction in its wake. You feel the dread among the characters as they struggle with how to deal with the machine, all while Windom gives a terrific performance as a broken man driven to suicidal actions if it means saving more people from the machine's destructive course.
4 "The City on the Edge of Forever"
After accidentally injecting himself with a high dosage of cordrazine, McCoy is driven into a mad frenzy and jumps through a portal known as Guardian of Forever (Bartell LaRue), which transports him back in time. Kirk and Spock jump to a point before his arrival to prevent Bones from changing the present, and wind up in New York City during the Great Depression. As they try to blend in and await the crazed doctor's arrival, Kirk bonds with Edith Keeler (Joan Collins), the idealistic owner of a soup kitchen who, according to history, dies tragically.
"The City on the Edge of Forever" was written by Harlan Ellison, the writer of I Have No Mouth and I Must Scream, so it should be no surprise that the episode is full of fantastic writing. A major theme of the episode is sacrifice for the greater good, as Kirk must stop McCoy to preserve the timeline, even if it means allowing an innocent to die. Edith and Spock therefore act as the angel and devil on Kirk's shoulder, but not in the way you would expect: Spock represents the cold, detached logic that tries to remind Kirk of his duty to the future, while Edith is the kind, idealistic demonstration of the best of humanity, who tempts Kirk to remain in the past.
3 "The Naked Time" (Season 1, Episode 4)
As the Enterprise travels to a dying planet to rendezvous with a Federation research base, they discover that the scientists are all dead and in illogical situations, such as one man wearing his clothes in the shower. A red liquid touches one member of the away team, and he later acts erratically towards the others. Pretty soon, this strange madness spreads throughout the ship, and the ship finds itself caught in the planet's atmosphere as more and more crew abandon their posts.
"The Naked Time" is an incredibly solid episode, with fantastic pacing and a really fun premise. Tension escalates in natural ways rather than feeling like mandatory drama, and it's incredibly entertaining to see how the crew acts while infected, with the highlights being Spock breaking down as he fails to control his emotions, and Sulu running bare-chested around the ship with a rapier. It's also an important episode in the history of Star Trek for being both the first use of the Vulkan nerve pinch, and the introduction of time travel to the franchise.
2 "Balance of Terror" (Season 1, Episode 14)
The Enterprise is sent to inspect the Neutral Zone when several Earth outposts suddenly go dark. They discover that the stations were destroyed by the Romulans—an offshoot of Vulcans who warred with the Federation a century ago—using a ship with advanced cloaking technology. What follows is a deadly game of cat-and-mouse as Kirk and the Romulan Commander (Mark Lenard) try to outfox and destroy the other.
"Balance of Terror" introduces the Romulans, one of the franchise's best antagonistic species, and Lenard, who would go on to play Spock's father, Ambassador Sarek. He does a brilliant job as the Romulan Commander, especially as he is caught between his desire to go home and his commitment to his duty that keeps him in battle with the Enterprise. Kirk himself also goes through the wringer as he struggles to find a way to defeat the Romulan ship, which leads to a fair amount of fantastic quotes as he interacts with his crew and opponent.
1 "Amok Time" (Season 2, Episode 1)
Spock begins acting irrationally and aggressively one day, while requesting that Kirk steer the Enterprise to Planet Vulcan. This is because he has entered pon farr, and unless he returns to Vulcan and mates, he will die. Kirk defies Federation orders to save his friend's life, but things become more complicated when Spock's chosen mate, T'Pring (Arlene Martel), invokes a fight to the death between Spock and her chosen champion: Kirk.
"Amok Time" is one of the original series' juggernaut episodes that changed the franchise forever. It expanded on Vulcan culture—including the iconic Vulcan salute and the phrase "live long and prosper"—demonstrated how dangerous Vulcan logic can become when used for less altruistic reasons, and highlighted the core friendship between Kirk, Spock, and McCoy. The duel between Kirk and Spock is also one of the show's most iconic moments, both due to the high emotional stakes of two best friends fighting to the death, and Gerald Fried's legendary music.
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