Episode Trivia


This is the only original series episode where Scotty addresses Kirk as "Jim".
First foray into the mirror universe. Major Kira Nerys and Dr. Julian Bashir would later find their way into the mirror universe in "Star Trek: Deep Space Nine's" episode "Crossover" where the Terran Empire had been conquered by the Klingon/Cardassian/Bajoran Alliance. The episodes "Through the Looking Glass", "Shattered Mirror", and "The Emperor's New Cloak" from "Star Trek: Deep Space Nine" as well as "In a Mirror, Darkly, Part I" and "In a Mirror, Darkly, Part II" from "Star Trek: Enterprise" would also deal with the mirror universe.
As would be later revealed in the "Star Trek: Enterprise" episode "In a Mirror, Darkly, Part I", the U.S.S. Defiant later seen in "The Tholian Web" would in fact slip into the mirror universe.
The scene of Lieutenant Marlena Moreau introducing herself to Captain Kirk in the "real" universe would later be incorporated (and altered to include Captain Sisko) into the "Star Trek: Deep Space Nine" episode "Trials and Tribble-ations".
Kirk asks the evil-Spock about the Halkan's prediction of galactic revolt. When did he hear that? The Halkans in his dimension never said any such thing (why would they?), and other than a brief chat that we saw where it was never mentioned, Kirk never talked to the Halkans in the mirror universe.
In the sickbay fight, evil Spock's hair noticeably changes (gaining curls!) when they switch to shots of Leonard Nimoy's stunt double.