Before Star Trek became one of the most famous science fiction franchises ever made, it was just a struggling NBC show trying to stay on the air. The original series premiered on September 8, 1966, and followed Captain James T. Kirk (William Shatner), Spock (Leonard Nimoy), Dr. McCoy (DeForest Kelley), and the crew of the USS Enterprise as they traveled through space in the 23rd century.
It ran for three seasons and aired 79 episodes, but during its original run, the ratings were never strong enough to make NBC fully confident in it. The last episode, “Turnabout Intruder,” which aired on June 3, 1969, wasn’t written like a big series finale, so fans didn’t get a true farewell to the show or its characters. Star Trek closed with a strange body-swap episode that is now often remembered as one of the show’s most awkward and awful endings.