Recap / Star Trek S1 E5 "The Enemy Within"
Kirk, Sulu and some unusually long lived Red Shirts are collecting specimens from Alpha 177 when someone falls down a hill and gets a boo-boo. He's beamed up, along with a strange, magnetic ore that he picked up in his fall. Shortly after, Captain Kirk beams up, feeling a little woozy. Scotty leads him away, even as Kirk warns him not to leave the transporter room unattended. What beams up next is... Captain Kirk! You can tell it's an evil Kirk! He's wearing eye liner and sweating like a pig!

So now,Kirk's got a doppelganger running about acting more like Captain Morgan than Captain Kirk. No one dares use the transporter now, so Sulu and company are left behind on a planet that gets well below 0 at night. And it seems that whatever happened to Kirk also happened to a little canine creature. One's a sweet little lap dog, the other... well, ever see that Tom and Jerry cartoon called "The Cat's Me-Ouch"?

Tropes for this episode include:

  • Attempted Rape: Poor Janice is subjected to this by Evil!Kirk.
  • Clear My Name: Certainly important to Good!Kirk.
  • Color-Coded for Your Convenience: Evil!Kirk wears the yellow command uniform. Good!Kirk wears his casual green shirt. That is, until Evil!Kirk realizes he can (temporarily) fool people by changing his shirt.
  • Dirty Coward: Evil!Kirk lacks Good!Kirk's courage (see Villainous Breakdown).
  • Early Installment Weirdness: It's a bit weird to see Spock call himself "half human, half alien," when for the bulk of the series he clearly identifies as Vulcan.
    • Sulu could have been brought aboard had they thought to use the shuttlecraft. The only reason they didn't think of it is because the concept of the Enterprise shuttlecraft hadn't yet been conceived for the show.
  • Enemy Within: Well, duh! Look at the ep's title!
  • Evil Me Scares Me: "I've seen a part of myself no man should see."
  • Evil Twin: Created by transporter accident.
    • This is a rare case where the evil twin isn't an imposter, but actually is the real person (albeit the negative, disagreeable side of that person).
  • First-Name Basis: Evil!Kirk tells Yeoman Rand to call him Jim, as he calls her Janice.
  • Gallows Humor: Sulu cracks a few jokes about just needing a coffee when it's a very real possibility they could die from cold.
  • Good Eyes, Evil Eyes: Evil!Kirk wears eyeliner and his eyes are always narrow and shifty.
  • Good Is Impotent: Evil!Kirk has been saddled with all of Kirk's willpower, determination, and aggression, and left without these traits Good!Kirk is rather meek, indecisive, and passive. But actually is played with a little, as Good!Kirk has Kirk's courage, while Evil!Kirk at heart is afraid.
  • Guyliner: Evil!Kirk wears it, as per the Excessive Evil Eyeshadow trope. He also puts on some make-up in attempt to hide the scratches Rand put on him.
  • He's Back: Kirk's halves are put back together and it's obvious he's survived the process, but the real "He's Back!" moment comes when he decisively says "Get those men aboard fast!"
  • He's Dead, Jim: After they attempt the re-merging with the creature, McCoy and Spock examine the limp form that beams up.
    Spock: It seems the shock was too much.
    McCoy: He's dead, Jim.
  • I Need a Freaking Drink: Evil!Kirk demands Saurean brandy when he enters sick bay. Later, Bones decides that both he and Good!Kirk need it.
  • Idiot Ball: Who exactly thought it was a good idea to have Yeoman Rand questioned about her attempted rape by the accused perpetrator?
  • Jekyll & Hyde: a transporter malfunction splits Kirk's good and evil sides.
  • Large Ham:
    Evil!Kirk: I'm Captain Kirk! I'm Captain Kirk! I'M CAPTAIN KIRK! IIIII'M CAPTAIN KIRRRRRK!!!
  • Literal Split Personality: Kirk of this episode is a famous example. It is learned that the "evil" side proved to be the side with the strength to make tough decisions, proving that both halves are needed for the whole to work. And the seemingly meek, passive "good" side turns out to have more courage than the other, whose angry defiance hides terror of losing independent existence.
    "Can half a man live?"
  • Mundane Utility: Sulu uses a phaser to heat up some rocks for warmth.
  • Must Have Caffeine: Sulu asks if it's possible for them to send down a pot of coffee. Possible, he just wants something hot. He would've settled for sake.
  • O.O.C. Is Serious Business: Never has it been more serious!
  • Out-of-Character Alert: Kirk is split into his good and evil sides by a transporter accident, which leaves several of the Enterprise crew stranded on a hostile planet. Spock feels a bad vibe when the evil Kirk, passing himself as the good one, walks onto the bridge. Then he declares that the men can't be saved and orders the ship to leave orbit, at which point Spock knows it's not the real one - since when would James T. Kirk leave his crew to die?
  • Panty Shot: Yeoman Rand does a brief one as she tries to get away from Evil!Kirk.
  • The Power of Hate: When Kirk gets split into Good!Kirk and Evil!Kirk, Good!Kirk is barely able to function because, as Bones points out, he needs the power of hate as well as love.
  • Ridiculously Cute Critter: Sulu finds something that looks like a mash up of a cocker spaniel, a unicorn and a baby dragon with some screwy looking antenna. And it's flippin' adorable! (When its evil half isn't trying to eat your face, that is.) What a pity that it dies in the end.
  • Shadow Archetype: The good-yet-indecisive Kirk and his evil-yet-effective twin: "I have to take him back... inside myself. I can't survive without him. I don't want him back. He's like an animal, a thoughtless, brutal animal and yet it's me. Me." Really though, both the good and evil Kirk are Shadow Archetypes to the real Kirk; he wouldn't want to be either one of them.
  • Shirtless Scene: Shortly beaming up, Good!Kirk feels a sudden urge to go change his shirt. The ladies (and Mr. Spock) get some eye candy, and there's a reason for the sudden Color-Coded for Your Convenience.
  • Take a Third Option: Spock explains how he uses this to live. His human and Vulcan natures are constantly in conflict, but he uses his intelligence to keep both in line and make them work together.
  • Tantrum Throwing: Evil!Kirk throws a fit when he can't get his way.
  • Technobabble: Spock's explanation of how the transporter was repaired comes off as this.
  • Understatement: Before beaming up, Kirk tells Sulu that the temperature on the planet gets down to some ridiculously low arbitrary temperature at night. Sulu replies, "That's nippy."
  • Villainous Breakdown: Evil!Kirk finally gives up when he breaks down, sobbing, "I don't wanna die!"
    "I don't wanna go back. I wanna LIIIIIIVE!!!!"
  • Warring Natures: Spock claims that his human side and his "alien" side are constantly doing this.
  • What the Hell, Hero?: McCoy gives this to Spock when he uses Kirk's situation to coolly analyze the roles of good and evil in human nature. Spock doesn't back away from the accusation, but does offer an apology of sorts to Kirk for his seeming to be uncaring.
  • Writers Cannot Do Math: No matter what scale you use, the temperatures given for the planet's surface mean Sulu's team would have frozen to death before the episode is even halfway over.