We recap ten defining episodes from 'Star Trek: The Original Series'

Star Trek: The Original Series was and remains the gold standard of the Trek franchise.

It was the first series in the cultural juggernaut, and it basically defined science fiction as we know it today.

With the third season of Star Trek: Discovery set to premiere in October, it’s a good time to reflect on the franchise.

What were the episodes that really encapsulated what each series in the Trek saga?

Bear in mind, these are not the “best” episodes of each series. But rather the episodes that convey what each series was all about.

That said, here are ten defining episodes from Star Trek: The Original Series.

Dr. Daystrom built a murder machine on 'Star Trek: The Original Series'

10. The Ultimate Computer, Season 2

Technology run amok is a tradition for Star Trek. Hell, it remains vital in modern Trek with the second season of Discovery and the first season of Picard.

Though TOS dealt with it before, the show’s stance on A.I. was never clearer than in ‘The Ultimate Computer.’

Captain Kirk (William Shatner) and the Enterprise is summoned by Starfleet Command to participate in a war games exercise. But it will be a unique one. The Enterprise will go from a crew of 400 down to a crew of 20. With all ship operations and decisions made by the new M-5 computer.

M-5 is the brainchild of computer genius Dr. Richard Daystrom (William Marshall). Kirk and Bones (DeForest Kelley) can’t imagine that a computer could take the place of a starship captain. Mr. Spock (Leonard Nimoy), of course, is as excited as a Vulcan can be that all decisions will be made strictly on the basis of logic.

But the situation becomes dire. M-5 was programmed with Daystrom’s own personality engrams. It recognizes its own superiority, and by the time the crew realizes they should just shut it off, the M-5 has learned to defend itself. Redshirt clean-up, aisle 5.

Worse, when it’s time for the war games, M-5 acts as though it’s the real thing. It unleashes the full firepower of the Enterprise on the hapless attack fleet.

It’s high-concept TOS morality at its finest, championing the resolve of human integrity over technological perfection.

Plus, it gives Kirk a chance to show off his greatest skill: Confusing a computer until it kills itself.


9. The Enemy Within, Season 1

If you’ve ever wondered with Star Trek: The Original Series has such a reputation for hammy acting, look no further than ‘The Enemy Within.’

A transporter accident (get used to those) results in two sides of Kirk’s personality being split into two beings. Good Kirk an Evil Kirk. So, doppelgangers. Get used to those, too.

The Good Kirk is imbued with Kirk’s best attributes. Kindness, compassion, empathy. And the Evil Kirk gets all the other stuff. Aggression, hatred, selfishness.

With the transporter broken, the Enterprise can’t retrieve their people from the planet. Back on the ship, the crew has another problem. They can’t just get rid of the Evil Kirk. It turns out Good Kirk is incredibly indecisive and pretty useless without his dark side.

Spock, being half human and half Vulcan, understands well Kirk’s predicament. He reminds Kirk that he himself has to force his two sides to coexist. Spock was never good at pep talks.

‘The Enemy Within’ is probably the first attempt by TOS to really delve deep into what Star Trek is all about. The human condition itself. It’s over-the-top and lacks any hint of subtlety. The episode has a point to make, and it’s willing to beat you over the head with a lead pipe until you get it.

Oh, and from a feminist perspective, there’s a subplot involving Evil Kirk and Yeoman Rand (Grace Lee Whitley) that’s extremely problematic.

Basically, it’s Star Trek: The Original Series in a nutshell.

Also, if you’ve never seen this episode, Shatner goes, well, full-Shatner in this one. It’s the one with the infamous scene of Evil Kirk screaming, “I’M CAPTAIN KIRK!”

Gold. Gold, I tell you.

Bele and Lokai from 'Star Trek: The Original Series'

8. Let That Be Your Last Battlefield, Season 3

Speaking of Star Trek: The Original Series beating you over the head with morality, there’s ‘Let That Be Your Last Battlefield.’

The Enterprise finds itself caught in the middle of an intergalactic policeman chasing his fugitive. Lokai (Lou Antonio) boards the Enterprise and begs Kirk for asylum, claiming he fears persecution from his pursuer, Commissioner Bele (Frank Gorshin).

At first glance, Kirk and the gang don’t get it. From all outward appearances, Lokai and Bele are members of the same race. One side of their face is bright white while the other half is pitch black.

But as Bele explains, Lokai and his people are black on the right side. Bele’s people are black on the left.

Naturally, to our enlightened 23rd century heroes, this is ridiculous. They’re the same race, just different colors. Getting this, 1960s America?!

In classic TOS fashion, Bele and Lokai’s battle rages throughout the Enterprise, forcing Kirk to take the ship to their guests’ homeworld.

But when Bele and Lokai return home, they discover a dead planet. The tensions between the two races have led to their world’s annihilation. Normally on TOS the two parties would realize the error of their ways and rebuild.

Instead, Bele and Lokai beam down to the surface, the last of their respective peoples. And they continue the fight.

Unsubtle and metaphor-heavy with ample scenery-chewing. It’s another episode of Star Trek: The Original Series that tells you everything you need to know about the show.

Kirk battles the Gorn in 'Arena'

7. Arena, Season 1

For those of you not terribly familiar with Star Trek: The Original Series, this is the one where Kirk fights the lizard guy.

The Enterprise responds to a distress call from a Federation colony. But when they arrive, they discover the colony has been completely wiped out by the Gorn. From all appearances, the Gorn are monstrous reptiles, capable of communicating only in snarls and growls.

After a brief ground battle, Kirk and the gang chase the Gorn ship across the system. The chase leads them into orbit of an uncharted planet, and both ships are fully prepared to destroy each other.

But, as happens often on TOS, it just happens to be home to beings with godlike powers.

Viewing the Enterprise and the Gorn as primitives, they resolve the situation themselves. Kirk and the Gorn captain are transported to the planet. And the local gods lay own the rules. The two captains will fight to the death. Whoever wins gets to go back to their ship and head home. The loser’s ship gets blown up.

Spock and the bridge crew get a closed circuit feed. For the first part of the fight, they watch their boss get his butt handed to him. Eventually Kirk proves his ingenuity, scrambling together raw material to build a makeshift cannon.

But during the course of the fight, Kirk learns that the Federation unknowingly settled on a planet in the Gorns’ space. The Gorn were simply protecting their territory.

When Kirk gets the advantage and has the opportunity to kill the Gorn captain, he refuses. This impresses the gods, and they let both ships go on their way.

Yet more classic TOS morality. The episode is all about not jumping to conclusions. And with a few of those nods to good old fashioned human resourcefulness that creator Gene Roddenberry liked so much.

The deformed Captain Pike in 'The Menagerie'

6. The Menagerie, Parts 1 And 2, Season 1

For decades, episodic television was just that. Episodic. What happened last week has no bearing on what happens this week.

For the most part, Star Trek: The Original Series didn’t concern itself much with world-building.

And even with ‘The Menagerie,’ the point was not to expand the Star Trek universe. It was more about getting mileage out of an unused pilot.

The first pilot episode for Star Trek, ‘The Cage,’ was rejected by NBC. Starring Jeffrey Hunter as Captain Christopher Pike, ‘The Cage’ told the story of Pike and the Enterprise answering a distress signal on planet Talos IV. Not long after their arrival, they discover it’s a ruse. Pike is captured for use in a zoo run by telepathic, illusion-conjuring aliens.

During the first season of TOS, ‘The Cage’ was unearthed and used for footage in ‘The Menagerie.’

Thirteen years after ‘The Cage,’ Captain Pike is paralyzed due to an accident, prompting Spock to break all the rules to get his old captain back to the Talosians. Spock is court-martialed for mutiny. But the Enterprise is on auto pilot and forced to travel to Talos IV anyway. Spock he uses images from ‘The Cage,’ telepathically beamed to the Enterprise by the Talosians, as his defense.

It’s an inventive way to get two episodes’ worth of material out of old footage, making ‘The Menagerie’ a showcase of the producers’ ingenuity. And, in retrospect, it was a cool way to provide a broader scope to the Trek universe. To recognize that the Enterprise had a captain before Kirk was the franchise’s first acknowledgement of legacy.

And boy, would they shake every bit of fruit that would come out of that tree. But TOS did it first.

The Romulan Commander defined his race on 'Star Trek: The Original Series'

5. Balance of Terror, Season 1

‘Balance of Terror’ introduced my personal favorite Star Trek: The Original Series villains, the Romulans.

A hundred years after the end of the Earth-Romulan War, the last time Starfleet and the Romulans had any contact of any kind, the Romulans fight their way into the Neutral Zone. An area of space established by treaty. Entry by either party means war.

Kirk and the Enterprise are the closest ship to the incursion (get used to that). And a submarine-like game of cat-and-mouse ensues. Made all the more difficult by the Romulans’ possession of a cloaking device, which renders their ship invisible.

Making matters more awkward, Spock is able to get an image of the Romulans’ bridge. This provides the first look humans have ever had at the Romulans. And guess what? They look exactly like Vulcans.

So you have Kirk and the Romulan Commander (Mark Lenard) matching one another move-for-move. And there’s the unspoken suspicion among the crew that Spock might be a spy. It’s a unique plot for Star Trek: The Original Series with its militaristic feel.

But, like the best of TOS, it ends on a hopeful note. The Romulan Commander doesn’t want another war, but it’s his duty to carry out the will of the state. He and Kirk even acknowledge to one another that, under different circumstances, they could have been friends.

‘Balance of Terror’ is 52 minutes of Star Trek: The Original Series that wrote the blueprints for every Romulan episode of every Star Trek spin-off to follow.

The TOS crew goes to the dark side

4. Mirror, Mirror, Season 2

So yeah. This is the episode where Evil Spock has a goatee.

Kirk, Uhura (Nichele Nichols), Scotty (James Doohan), and Bones are negotiating with a planet full of pacifists for the right to mine their dilithium. But the natives’ ethics won’t allow it on the remote chance that their dilithium might be used to take lives.

Both parties adjourn, and Kirk and company head home. But there’s a pretty rough ion storm going on upstairs. And during the beam-up, the gang winds up in an alternate universe. Where the I.S.S. Enterprise is the flagship of the Terran Empire and where Kirk got his command and status by murdering Pike.

And where Spock has a goatee.

The landing party has to blend in long enough to find a way back to their own universe. And while they’re there, everybody gets a chance to ham it up. Sulu (George Takei) is a gestapo-like security chief with a major crush on Uhura. Also, he’s not a “no means no” kind of guy.

Chekov (Walter Koenig) tries to get a promotion by killing Kirk. But he’s thwarted by Kirk’s personal security guards. Which, in turn, results in Spock throwing Chekov in the agony booth, designed to keep prisoners in constant, well, agony.

But, it’s TOS. We can’t head home before the Kirk gives a speech. He recognizes that Evil Spock is really like the Prime universe Spock. So Kirk offers up logic. Kirk leaves Spock with the idea to overthrow the Empire and establish a more peaceful government.

High concept sci-fi, pseudo-science, hammy acting, and pleas for morality. And stage beards. The best qualities of Star Trek: The Original Series.

'The Trouble With Tribbles' is one of the best episodes of 'Star Trek: The Original Series'

3. The Trouble With Tribbles, Season 2

Comedy episodes in Star Trek can go any number of ways. Most of them bad.

Star Trek: The Original Series only did a handful of episodes with a light touch. One of the criticisms of TOS in general was that it took itself too seriously. That does not apply to ‘The Trouble With Tribbles.’

A space station sends out a priority one distress signal, which the Enterprise answers. But when they get there, it turns out the distress is that the space station needs a starship to guard a Federation shipment of grain.

Sounds silly, but the grain is critical to the Federation colonizing a disputed planet. A planet that the Klingons have their eyes on, too. Now mortal enemies are in the same place with an entire planet’s fate in the balance.

So why is this a light-hearted episode? Because in the background, the Enterprise crew buy some cute critters, the titular Tribbles, as pets. Only to find out that they reproduce at an alarming rate. To the point that the ship is swarming with them.

But the highlight is Kirk and Spock getting a chance to play comedian and straight-man, respectively. It’s like the writers took a step back from TOS to ask, “Can we get some fun out of this show?”

And as it turns out they could, in a big way. Star Trek continued to get mileage out of ‘The Trouble With Tribbles’ for decades. There was a direct sequel on Star Trek: The Animated Series. And Star Trek: Deep Space Nine revisited the episode as part of Star Trek‘s 30th anniversary.

Turns out Tribbles are the TOS gift that keeps on giving.

Best friends at odds in 'Amok Time'

2. Amok Time, Season 2

Every season of Star Trek: The Original Series gave us a glimpse at who Spock was. What made him tick? How did he reflect his people, the Vulcans?

‘Amok Time’ delved deep into Spock’s internal conflict. And it gave us a look at Vulcan culture in inventive ways.

As the episode begins, Spock has been a little cranky of late. He’s not leaving his room very often, he’s threatening Bones, and when Nurse Chapel (Majel Barrett) tries to bring him a bowl of soup, he chucks it at her.

Spock can’t tell Kirk why, but he needs to get to Vulcan. Unfortunately, the Enterprise has to be on-hand for a big diplomatic function. Vulcan will have to wait. Until Bones clues Kirk in about what’s really going on with Spock. He’s dying. Spock explains that he’s basically going through Vulcan mating season. And if he doesn’t get home, his suppressed emotions will boil over and kill him.

So Kirk defies Starfleet to save his friend. But when they get to Vulcan, Spock’s mate throws a wrench into the works. She invokes a Vulcan ritual where Spock must fight a champion of her choosing to the death. And she chooses Kirk.

Bad week for Captain Kirk. First his friend is dying. Then he’s risking getting fired to save him. Now maybe Spock’s girl has a crush on him? But he has to fight him to the death.

If ever there was a week for the captain to work from home.

‘Amok Time’ is a staple of TOS. Not just because of the iconic fight (you’re humming the music now, aren’t you?). But because Star Trek: The Original Series took steps when it could to explore something about its universe.

Kirk and Edith in the best episode of 'Star Trek: The Original Series'

1. The City on the Edge of Forever, Season 1

This one holds up.

‘The City on the Edge of Forever’ is a TOS episode that still ranks among the franchise’s greatest accomplishments. And with good reason.

The Enterprise flies through a storm, and Sulu is critically injured. The only way Bones can save him is with an experimental drug with dangerous side effects. It works on Sulu, but the storm rocks the ship again. And Bones accidentally injects himself with the full dose.

A delusional Bones races to the transporter room and beams to the planet. Kirk and Spock follow, but Bones escapes through a portal – the Guardian of Forever. Instantly, they can’t contact the Enterprise. Bones changed history.

Kirk and Spock give chase and end up in 1920s New York. They hunt for Bones and try to blend in, and Kirk falls in love with a social worker, Edith Keeler (Joan Collins). But Spock does some research and discovers something horrible.

Bones somehow prevented Keeler’s death. Keeler became an adviser to FDR and delayed US entry into World War II. The Nazis conquered Earth. No Enterpise, no Starfleet, no future.

Kirk faces with the biggest dilemma of his life. Can he let the woman he loves die to save the future?

The Trek franchise hadn’t even coined the phrase, “The needs of the many outweigh the needs of the few.” Here, TOS puts that concept front-and-center.

All images courtesy of startrek.com.