The first episode I saw (sometime back in 1972 or 1973) was Space Seed
I literally never heard of Star Trek to that point (I was just a wee lad). I remember them beaming onto the Botany Bay
at the beginning, and being confused as to what that was (the beaming over, I mean). I was also enthralled with Spock.
I remember getting my older brother to watch it with me. He knew about Star Trek, and explained some if it to me.
I agree with those who say one of the best starter episode would be Balance of Terror
I do NOT agree that The Trouble with Tribbles
would be a good starter episode. To really appreciate the humor of that episode, you need to be familiar with the characters to begin with, since each character was playing a bit of a caricature of himself, for example:
- Shatner further exaggerating his already staccato delivery for some of his lines.
- Spock with the classic one-liners ("He heard you; he simply could not believe his ears"
- Scotty with his defending the ship's honor, and with his love of everything engineering.
- Doctor McCoy being a bit too amused with his zoological study of the Tribbles.
- Chekov's Russian reference and his over-exuberance.
Without having a baseline expectation of each character to begin with, the jokes made in the episode can be lost.
So, I say:
Balance of Terror
These are among the best "stand-alone" episodes (from a character standpoint).