1. Arena Kirk is sent to battle the Gorn while his crew watches from the Enterprise. This is easily one of the best fight scenes to ever air on television. To watch the full episode click here.

2. The Naked Time The crew of the Enterprise is struck with a strange affliction that lowers their inhibitions. Funniest moment: Sulu fencing shirtless through the hallways in a stunning display of heterosexuality. Best moment: Spock's emotional breakdown which was improvised completely by Nimoy. To watch the full episode click here.

3. Amok Time Spock must return home to Vulcan to undergo a brutal Vulcan mating ritual in which he must mate or die. He and Kirk engage in a fight to the death at the request of Spock's mate, and only once Spock thinks he's killed the captain is the ordeal over. Best moment: Spock actually smiles upon realizing that Kirk is alive. Watch the full episode here.

4. The Trouble With Tribbles This lighthearted Star Trek episode aired on December 29th, 1967 and was billed as Star Trek's Christmas episode. It features the arrival of the notoriously cute Tribbles who multiply like space bunnies in heat and hate Klingons. Watch the full episode here.

5. City on the Edge of Forever Guest starring Joan Collins as Edith Keeler, this is one of the most widely acclaimed episodes of the original series. This episode is also notorious for featuring the first swear word uttered on national TV by Captain Kirk who, after returning from his harrowing experience in the past, turns to his crew and says "Lets get the hell out of here." Watch the full episode here.

6. Mirror, Mirror This episode marks the origin of the so-called "Beard of Evil stereotype so often parodied on shows like The Big Bang Theory and Futurama. Watch the full episode here.

7. A Piece of the Action Kirk and Spock as 1920s gangsters. Need I say more? Watch the full episode here.

8. Journey to Babel We meet Spock's parents! Spock's mother tells embarrassing stories about Spock's childhood! Someone tries to assassinate Spock's father! Kirk is attacked! McCoy finally gets the last word! Watch the full episode here.

9. Plato's Stepchildren Sticking to their promise to boldly go where no man has gone before, Star Trek set another TV milestone when it aired the first interracial kiss between Kirk and Uhura. Sure the two were under mind control at the time, but a kiss is a kiss is a kiss. Unfortunately, in re-watching the episode with a more modern perspective, the kiss is often overshadowed by the bizarre nature of the clip I included above. Captain Kirk pretending to be a horse while a little person rides on his back. WTF, indeed. Watch the full episode here.