"Space Seed" gives rise to one of "Star Trek's" greatest villians, the genetically enhanced super-solider Khan.
The episode's real strength is in the setup between the characters: both the Kirk-Khan and the Kirk-Spock dynamics. Plus, it poses questions about the human fascination with and admiration of tyrants and ruthless dictators.
But, more importantly, this episode is essentially a prelude for the best "Star Trek" movie of all time, "The Wrath of Khan."
Memorable quote:
Kirk: He was the best of the tyrants and the most dangerous. They were supermen in a sense. Stronger, braver, certainly more ambitious, more daring.
Spock: Gentlemen, this romanticism about a ruthless dictator is...
Kirk: Mr. Spock, we humans have a streak of barbarism in us. Appalling, but there, neverthless.