The Enemy Within
Hands down this is the best overall episode I've watched so far.
Kirk, Sulu, and the red shirts are down on this rocky planet that looks very familiar to all the other rocky planets they've been on. They're collecting specimens which include a shaggy terrier dog with a unicorn horn. Red Shirt #3452-F6 aka Fisher falls down, cuts his hand open, and gets some weird yellow ore on his clothes. Kirk has him beamed back to the Enterprise, only Scotty has trouble getting him through the transporter.
(It was at this point Missus RC blurted out, "If they ever invent a transporter, I'm not getting in it because the damned thing never works!")
Kirk follows shortly after, but comes through all dizzy. Scotty helps him to his quarters and while the transporter room is empty another Kirk beams through! This Kirk is all shifty-eyed like he just shoplifted something from Macy's and is trying to get past the security guard.
Over is sick bay, Bones is finishing up with Fisher the Red Shirt. Shoplifter Kirk comes in and demands "Saurian Brandy" as if he's been hitting the bottle since about 8am. Bones, thoroughly confused hesitate and almost gets a Wino James T. Kirk whoop ass laid on him. He gives him the bottle.
At the behest of Bones, Spock goes to see the real Kirk who's been napping through all this and tells him he's being a dick. Kirk tells Spock that Bones is playing a trick on him. At this point, Scotty calls them to the transporter room and shows them two unicorn horn dogs. One is docile. The other is sort of, I don't know, totally evil.
Scotty shuts down the transporter to fix it which REALLY sucks for Sulu and the Red Shirts. As it turns nightfall, the temperature on this familiar looking rocky planet drops to 175 degrees below zero.
Meanwhile, Wino Kirk heads over to Yeoman Rand's room, lays down some trash talk about "their true feeling for each other" then attempts to rape her. Rand is either sober or lucky enough to fend him off and scratch his face. Aha! Now we can tell Date Rape Kirk from the REAL Kirk! Too bad Date Rape Kirk beats the shit out Red Shirt the Fisher and steals his phaser.
Speaking of the real Kirk, he's having trouble thinking straight, making decisions, and being anything more than a stoned whiner. Having figured out there's an imposter on board, Spock gets the crew looking for him. Eventually, they corner Armed & Dangerous Kirk in Engineering and after a tense back and forth with real Kirk: Vulcan Neck Pinch! Who's a badass mutha-Vulcan?
Sulu is still freezing his ass off despite using his phaser to heat up rocks (which I thought was a pretty cool idea) and man-bagging with the Red shirts.
Sulu: "We have to stay close to keep warm! You, put your hands down my pants."
Red Shirt #8765-R8: "What?"
Sulu: "It'll keep your warm. My phaser will warm up your rocks, if you know what I mean."
Real Kirk is deteriorating rapidly. Turns out that the transporter accident didn't create a new Kirk. It split Kirk into two beings. One who is Rational, intelligent, yet indecisive. The other is a shoplifting, drunken, weapon carrying, date rapist. Talk about your dark side. They have to merge them back together to form Devestator, the most powerful Decepticon! Only they test it with the dogs which while coming back through remerged also come back stone dead.
It's at this point, Bones first utters his trademark line, "He's dead, Jim."
Kirk has a choice to make. Take a chance on dying or take more time to do it right and Sulu and the Red shirts freeze to death in man bag ecstasy. He's obviously not thinking straight because he decides to release Evil Kirk who over powers him and scratches his face. Oh no! Now we can't tell them apart.
Evil Kirk goes to the bridge and orders them to leave Sulu and the Red Shirts behind. Then Spock and Bones show up with Real Kirk OR IS IT!?!?!?!? The Kirks confront each other. Evil Kirk has a meltdown, Good Kirk is stoned. They realize they need each other. Back to the transporter room and the Twilight and Let the Right One In threads are merged!!! Even though they seem completely different, they can't exist without each other!
Sulu and the Popsicles are saved. Kirk accepts his duality. Saurian Brandy for everyone. (Except Yeoman Rand. Drunk bitch.)