10 Most Important Episodes Of Star Trek: The Original Series
5. Space Seed (1.22)
1982's Star Trek II: The Wrath of Khan is largely considered the best of the Star Trek feature films and its catalyst came in the form of the 1967 season one episode of TOS, Space Seed.
The episode follows the crew of the Enterprise as they discover a centuries-old ship floating through space, which, as it turns out, is carrying cryogenically frozen, genetically enhanced "supermen." Their de facto leader and the first one to be unfrozen by the Enterprise crew is a man named Khan, played by the late Ricardo Montalbán. Khan plays along with at first, before seducing the ship's historian, Marla McGivers, and with her aid, stages a mutiny with his personal army.
Ultimately, however, he is defeated and he, McGivers, and his people are sentenced to inhabit a barren planet and fend for themselves. This, of course, directly sets Wrath of Khan's plot into motion, in which Montalbán reprises his role as the titular character, who would go on to become arguably the most notorious of all Star Trek villains, as it was his plot that resulted in Spock's death at the end of the stellar film.
Of course, Khan's story would also eventually be used as the basis for the critically acclaimed 2013 film, Star Trek Into Darkness.