"Mirror, Mirror" airs
"Mirror, Mirror" is an episode of Star Trek: The Original Series.
It is a second-season episode, #33, production #39, and was broadcast for the first time on October 6, 1967. It was repeated on April 12, 1968. It was written by Jerome Bixby and directed by Marc Daniels.
The episode introduces the alternate reality "Mirror Universe" concept in Star Trek for the first time. The episode has a transporter mishap swapping Captain Kirk and his companions with their evil counterparts in a parallel universe. In the so-called Mirror Universe, the Enterprise is a ship of the Empire rather than the Federation, promotions are earned by assassination, and Mr. Spock has a goatee.