Mirror, Mirror (Star Trek)

Mirror, Mirror was an episode of the original series of Star Trek. It introduced the Mirror Universe. It was broadcast for the first time on June 10, 1967, and was written by Jerome Bixby.

Due to a transporter accident, Captain Kirk's landing party was swapped with a similar landing party from a parallel universe. This particular universe was one very similar to the one depicted in the show; with the exception that the peace-loving United Federation of Planets had been replaced with a brutal Terran Empire. The ISS Enterprise was in exactly the same place as the USS Enterprise, and was captained by a sadistic alternate version of Captain Kirk, whose first officer was a Mr. Spock with a beard.

The show ends with Kirk persuading the mirror Spock to try and forment some kind of revolution in the mirror universe. The episode is followed up in Star Trek: Deep Space Nine episodes, starting with Crossover.