Few episodes of Star Trek are quite as iconic as Mirror, Mirror. First broadcast in 1967 as part of the Original Series' second season, it's an episode that even people who aren't fans or even casual viewers of Star Trek will immediately know. After all, it's been referenced not just in other science fiction series such as Stargate SG-1, but also in shows like South Park. So what is it about the episode that makes it so memorable?
A large part of it is undoubtedly the parallel universe concept at the heart of the episode, referenced and parodied time and again. Even back in 1967 when this episode first aired, the idea wasn't a new one by any means with writers, including this episode's writer Jerome Bixby, who with his own earlier short story One Way Street had already explored the idea quite a bit. Bixby used that earlier short story as a jumping off point of sorts, with further rewrites being done by Gene Roddenbery, D.C. Fontana and Gene Coon, before the episode reached reached production. What seems to have been different here was that this was perhaps the first to take the idea and apply it to characters and situations in an established series. Not only that, but it presented what might be considered “evil” versions of those established elements long before it was the norm (Doctor Who, already nearly four years old when this episode first aired, would do it three years later in Inferno). That, combined with decades of re-runs and Star Trek's ever growing fan base, has helped to establish Mirror, Mirror as perhaps the definitive depiction of a parallel universe in popular culture.
Well that and Spock's beard. Let's be honest: that's what people usually remember about this episode. As Friends would put it, this is “the one with Spock's beard.” The parallel universe concept needed something visual to establish it early on and, if the viewer didn't notice that the crew beaming back aboard the Enterprise were wearing different uniforms, then they would definitely notice the normally clean shaven Vulcan sprouting a goatee beard. The sight was (and indeed remains) a great visual image and a shock to those viewing the episode in 1967 and in the decades to come. If you doubt it's cultural impact, just remember that it even inspired a band name at one point.
The episode's parallel universe concept means that the cast can do things they normally would never get to do. Spock's beard may be a great visual image, but it also tells us that this isn't the Spock we've come to know and Leonard Nimoy's performance proves that as well. The Mirror Spock is every bit as logical as his “normal” self, but in this universe where there's an ever conquering Empire instead of a benevolent Federation, that logic has been turned to a cold and calculating level. When this Spock threatens Kirk and the Mirror Sulu late in the episode, he does so with a sense of cold menace that seems almost unthinkable from the Spock we've come to know and love. That's true of the entire cast from the normally likable Chekov attempting to assassinate Kirk, to Sulu's advances on Uhura, right down to the brief glimpse we get of the Mirror Kirk trapped in the “normal” universe.
Then there's the four members of the landing party who swap places with their counterparts in the Mirror Universe. Kirk, McCoy, Scotty and Uhura are the proverbial fish of water who are trying to fit into an environment for which they are ill-suited. Kirk, as the lead character, is the episode's focal point and the one upon which we get the majority of our exposure to life in this universe. Shatner's performance here is one of his best as he deals with trying to avoid annihilating the Halkan's to his dealings with the episode's female guest character Marlena (Barbara Luna) and his trying to convince Mirror Spock to seek another way. Almost the entire landing party though deals with some trouble, from Scotty's attempting to sabotage the phasers which arouses suspicions, to Uhura dealing with the unwelcome advances from Sulu. From an acting point of view the episode is one of the most memorable, and arguably one of the best, of the entire Original Series era.
Also of mention is the production design and costumes. The redressing of familiar Enterprise sets and corridors, often done subtly, helps to reinforce the Mirror Universe setting with slight changes and the more obvious addition of the Empire's emblem of the Earth and dagger to the bridge set. The costumes also help to reinforce the notion as well, with Kirk's and especially those costumes used for female characters, while others are more often than not just adaptations of those normally used. Those adaptations though, in both sets and costumes, work because it puts the viewer in familiar territory where it's the characters that are different, not the setting (plus it saves the production money).
In the end, it isn't hard to see why this is one of the most iconic of all Star Trek episodes. The Mirror Universe concept, and especially how it's represented visually, remains striking and recognizable nearly fifty years later. Plus the acting is never less than interesting while the production design and costumes help to sell the parallel universe in ways both subtle and obvious. It's no wonder then that this episode has been referenced and parodied so much, as well as often being returned to in Trek itself. And long may it continue to be so...
Matthew Kresal lives in North Alabama where he's a nerd, doesn't have a southern accent and isn't a Republican. He's a host of both the Big Finish centric Stories From The Vortex podcast and the 20mb Doctor Who Podcast. You can read more of his writing at his blog and at The Terrible Zodin fanzine, amongst other places.