Star Trek: The Next Generation never did a Mirror Universe episode, and that ultimately worked in the show’s favor. Star Trek’s Mirror Universe first debuted in the classic Star Trek: The Original Series episode, “Mirror, Mirror,” in which Captain James T. Kirk (William Shatner) and some of his crew find themselves in a dark alternate universe that mirrors their own. In the Mirror Universe, the ISS Enterprise serves the Terran Empire instead of the USS Enterprise as part of the United Federation of Planets’ Starfleet. Crew members are tortured when they make a mistake and the chain of command is often determined by officers murdering their superiors.
Despite the divergence of events in Star Trek’s Prime Universe and the Mirror Universe, many people ended up in the same place in both realities. For example, the entire crew of the USS Enterprise was the same in both universes, but their personalities were drastically different. Simply put, the Mirror Universe is a world of opposites, although Spock (Leonard Nimoy) is logical in every universe. While the Mirror concept worked well for a one-off story with Captain Kirk and his Enterprise crew, the Mirror Universe would have felt out of place on Star Trek: The Next Generation for a number of reasons.
Captain Jean-Luc Picard (Patrick Stewart) and the cast of Star Trek: The Next Generation represent the most moral Star Trek crew, and “evil” versions of those characters would have felt cartoonish. The Mirror Universe worked with the campy tone of Star Trek: The Original Series and Kirk was already an emotional Captain, so it wasn’t that hard to imagine an evil version of him. TNG, on the other hand, had a more serious and optimistic tone, and an evil Captain Picard would have likely been either too dark or too over-the-top. TNG did tell alternate universe stories, such as “Yesterday’s Enterprise” and “Parallels,” but they did it in a way that was new and unique rather than rehashing TOS‘ Mirror Universe concept.
Although Star Trek: The Next Generation had some callbacks to Star Trek: The Original Series in its early seasons, Star Trek creator Gene Roddenberry wanted to distance TNG from TOS. “Mirror, Mirror” is generally regarded as one of classic Star Trek’s best episodes, and it would have been difficult for any TNG episode to live up to that. Despite not doing a Mirror Universe episode, TNG found other ways to allow its actors to play different, and even evil, versions of their characters. Lt. Commander Data (Brent Spiner), for example, faced off against his evil twin brother Lore more than once, and multiple characters were possessed by alien entities.
Star Trek: Deep Space Nine had five Mirror Universe episodes, beginning with DS9 season 2, episode 23, “Crossover.” This episode revealed that Mirror Universe Spock had reformed the Terran Empire after Captain Kirk and his crew visited there in “Mirror, Mirror.” Although his reforms initially proved successful, they led to the occupation of the Empire by the Klingon-Cardassian Alliance, which then became the dominant power. In the Mirror Universe, Terok Nor (space station Deep Space Nine) was commanded by Intendant Kira Nerys (Nana Visitor), and Nana Visitor clearly had fun playing an evil version of Kira. However, with its overly sexualized characters and general campiness, the Mirror Universe storyline offered diminishing returns after the novelty wore off.
The Mirror Universe made more sense combined with the darker tone of Star Trek: Discovery, but it sometimes felt like too much for a Star Trek show. Still, the Mirror Universe of Discovery did provide the characters of Captain Gabriel Lorca (Jason Isaacs) and Emperor Philippa Georgiou (Michelle Yeoh), two of Star Trek’s best new villains. After its appearance in multiple Star Trek shows, the Mirror Universe began to feel too much like a gimmick. It’s a concept that works better when used sparingly, and it would have felt tonally out of place on Star Trek: The Next Generation.
Star Trek: The Next Generation, Star Trek: Deep Space Nine, Star Trek: Enterprise, & Star Trek: Discovery are available to stream on Paramount+.