10 Classic ‘Star Trek: The Original Series’ Episodes—Plus 3 Fans Love to Debate

What better way to celebrate the 60th anniversary of the original Star Trek than by looking back at the series itself? What follows is a behind-the-scenes guide to 10 standout episodes from the 1966–69 show—plus 3 episodes that miss the mark.

10 classic ‘Star Trek: Original Series’ episodes

These, it should be emphasized, are not the 10 greatest episodes—just 10 that work exceptionally well. (As a result, some of these selections may fall outside the usual list of fan favorites!)

Season 1, Episode 3: ‘Where No Man Has Gone Before’

The second Star Trek pilot—and the one that ultimately sold the series. Just as important, it brought William Shatner’s Captain Kirk together with Leonard Nimoy’s Mr. Spock, who had previously served under Jeffrey Hunter’s Captain Pike in “The Cage.”
LEONARD NIMOY: “Bill Shatner’s broader acting style created a new chemistry between the captain and Spock, and now it was quite different from the first pilot. The Bill Shatner Kirk performance was the energetic, driving performance, and Spock could kind of slipstream along and make comments, give advice and give another point of view.”
DAVID GERROLD (writer): “If you look at Spock with his mom or dad, it’s very ponderous. But Spock working with Kirk has the magic and it plays very well.”

Season 1, Episode 14: ‘Balance of Terror’

A taut thriller in which the Enterprise and a Romulan warbird engage in a deadly game of cat-and-mouse—essentially a World War II submarine story set in space. It also marks the introduction of the Romulans. “It was a matter of developing a good Romanesque set of admirable antagonists that were worthy of Kirk,” explains writer Paul Schneider. “I came up with the concept of the Romulans, which was an extension of the Roman civilization to the point of space travel.”
VINCENT MCEVEETY (director): “They were very heroic characters pitted one against the other, and it dealt with the length to which people would go for their honor.”

Season 1, Episode 22: ‘Space Seed’

The first appearance of Khan Noonien Singh, the genetically engineered superman portrayed by Ricardo Montalban, who would later reprise the role in 1982’s Star Trek II: The Wrath of Khan.
RICARDO MONTALBAN (actor): “Khan was a character that was bigger than life. He had to be played that way. He was extremely powerful both mentally and physically, with an enormous amount of pride. But he was not totally villainous. He had some good qualities. I saw a nobility in the man that, unfortunately, was overridden by ambition and a thirst for power.”
CAREY WILBUR (writer): “Interestingly, the episode’s roots trace back to the 1950s children’s sci-fi series Captain Video. We did some very far-out things on that show, including the popular idea of people being transported in space while in suspended animation. So I had this idea that I revived from Captain Video, because I thought it was time to do it again. It was a crazy story where we did the legend of men being turned into beasts, and our villainess had been transported from the days of Greek mythology to the future. So in doing ‘Space Seed,’ we took away the mythological powers and replaced them with a genetically altered human being.”

Season 1, Episode 23: ‘A Taste of Armageddon’

Kirk and Spock find themselves mediating a centuries-long war fought entirely by computers, with designated victims willingly reporting to disintegration chambers to preserve their societies. Kirk ultimately destroys the system, forcing both sides to confront the true consequences of war.
DOROTHY FONTANA (story editor): “[Producer] Gene L. Coon did a rewrite on that. I think some of the things he added really had a lot to do with the character of Kirk. It was Gene who wrote the speech at the end that man has a reputation as a killer, but you get up every morning and say, ‘I’m not going to kill today.’ It was one of those things that began to identify Kirk far more solidly than we had before.”

Season 1, Episode 25: ‘The Devil in the Dark’

The Enterprise investigates a mining colony plagued by a mysterious creature killing workers. The truth reveals something far more complex: the Horta is a mother protecting her eggs from destruction.
DAVID GERROLD: “This episode really gets to the heart of what Star Trek was. Here you had this menace, but once you understand what the creature is and why it’s doing what it’s doing, it’s not really a menace at all. We end up learning more about appropriate behavior for ourselves out of learning to be compassionate, tolerant and understanding.”

Season 1, Episode 28: ‘The City on the Edge of Forever’

Widely regarded as one of the greatest episodes of any version of Star Trek, this story sends Kirk and Spock back to 1930s New York in pursuit of a deranged McCoy. There, Kirk falls in love with Edith Keeler—a woman history insists must die.
HARLAN ELLISON (writer): “In the original script, Kirk attempts to save her and is physically stopped by Spock. All I was concerned about was telling a love story. I made the point that there are some loves that are so great that you would sacrifice your ship, your crew, your friends, your mother, all of time and everything in defense of this great love. The TV ending, where he closes his eyes and lets her get hit by the truck, is absolutely bulls**t. It destroyed the core of what I tried to do. It destroyed the extra human tragedy of it.”

Season 2, Episode 4: ‘Mirror, Mirror’

Kirk, McCoy, Scotty and Uhura are transported to an alternate, or “mirror,” universe where advancement comes through assassination and brutality. While searching for a way home, Kirk attempts to influence this darker version of Spock.
JEROME BIXBY (writer): “I wanted to do a parallel universe story. I had already done a fiction story called ‘One Way Street’ and I thought that would make a good Star Trek. The universe I created was a very savage counterpart, virtually a pirate ship into which I could transpose a landing party.”

Season 2, Episode 15: ‘The Trouble With Tribbles’

The episode that introduced tribbles—adorable, rapidly multiplying creatures—and proved Star Trek could successfully embrace comedy.
 DAVID GERROLD: “When I wrote the script, I looked at it as an honor and a responsibility, and I set out to write the very best Star Trek episode ever made.”
JOSEPH PEVNEY (director): “I thought David Gerrold made a hell of a contribution. My biggest contribution was getting the show produced, because there was a feeling amongst the people involved that we shouldn’t do it. It was a comedy and we had no business doing outright comedy. I certainly wanted to treat it as such, because that’s the way it was intended. It was highly successful in terms of audience appeal and it turned out fine with Bill Shatner doing bits he loved to do. The premise was humorous as hell.”

Season 2, Episode 17: ‘A Piece of the Action’

One of the series’ most playful entries, this episode finds the Enterprise on a planet modeled after 1920s Chicago, where gangsters rule.
DAVID HARMON (writer): “I felt that our western civilization is based on a Judeo-Christian ethic, so what I did in this episode was say that suppose a ship crashed, and the people on the planet salvaged a book called The Life of Al Capone, which they treated as their version of The Bible, and from which they built their own society.”
JAMES KOMACK (director): “Spock and Kirk came down with this great intellect and great intelligence that they possess, and they were dealing with monkeys. These guys had an I.Q. of about room temperature, and it was funny to watch Kirk and Spock stare at them, because they were just so ludicrous. They had this book they revered, they were mobs, they were taking over cities. Their brains just weren’t working that well. That was a lot of fun.”

Season 2, Episode 26: ‘Assignment Earth’

The second season finale doubles as a backdoor pilot for a potential spin-off centered on Gary Seven (Robert Lansing), an alien-trained human operating on 1960s Earth.

MARC DANIELS (director): “It was interesting trying to balance the episode between the regular crew and the Gary Seven character. It was also difficult because we came back to the present and it’s always a dangerous idea to take the Star Trek characters into the present. Suddenly, you’re in a very tangible situation. The show’s reality becomes that much harder to sustain.”
ROBERT LANSING (actor): “What Gene Roddenberry had done was go to futurists and scientists and ask them what advanced societies out in space might do towards more primitive societies like ours. One of the futurists said that they would probably kidnap children from various planets, take them to their superior civilization, raise them, teach and enlighten them, and then put them back as adults to lead the worlds in more peaceful ways. That was the idea behind Gary Seven.”

Bonus: 3 not-so-great episodes of ‘Star Trek’

Season 3, Episode 1: ‘Spock’s Brain’

Often cited as the worst episode of the series—and not without reason—this story literally revolves around the theft of Spock’s brain.
DAVID GERROLD: “The history of Star Trek is management by crisis. I think somebody called up Gene L. Coon and said, ‘We need a script in a hurry, can you do it?’ And he did it under a pen name. I don’t think he deliberately set out to write that show seriously. I don’t think there’s any way you can take that episode seriously. You’ve got to take it as a joke. What’s the stupidest science fiction idea to do? What if somebody stole Spock’s brain? I think Gene had that kind of sense of humor to do that sort of impish thing. He had an irreverent sense of humor and I think he wanted to poke Star Trek because someone was taking it too seriously.”

Season 3, Episode 20: “The Way to Eden”

Space hippies hijack the Enterprise in search of a mythical paradise that proves deadly.
FRED FREIBERGER (producer): “I didn’t like it at all and I don’t blame Dorothy Fontana’s original story. We probably did it all wrong. I’m unhappy to take the blame for that one, but there’s no one else to blame.”
ARTHUR HEINEMANN (writer): “I wrote some songs that the hippies sang. As a matter of fact, I get a royalty for it. About once a year a check comes for $3.47.”

Season 3, Episode 24: ‘Turnabout Intruder’

The final episode of the series sees Kirk’s body taken over by Dr. Janice Lester—an idea widely criticized for its execution and themes.
FRED FREIBERGER: “I have to tell you, Shatner is a very creative guy. When I say creative, I mean he’s willing to try anything. He loved ‘Turnabout Intruder.’ Frankly, I was a little concerned when Gene Roddenberry came up with the story. When I originally read it, I had said to Gene, ‘I wonder what Shatner is going to say about this,’ and Gene said he wouldn’t have any problem with it. He was right. When I mentioned it to Shatner, he just loved the idea.”

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