First appearing in the Star Trek: The Original Series episode "Mirror, Mirror," which first aired on October 6, 1967. This episode introduced the Mirror Universe and featured an evil, goatee-wearing version of Spock. Unlike his regular counterpart, Mirror Spock is the first officer of the ISS Enterprise and a key figure in the Terran Empire's hierarchy. Mirror Spock is initially a loyal, calculating, and ruthless officer, however, after interacting with Kirk's version of Spock, Mirror Spock is deeply influenced by Kirk's logical appeal to reform the empire, eventually rising to commander and implementing significant, peaceful changes within the empire.