Star Trek’s Biggest Crossover Caused By Kirk’s Biggest Mistake

By Chris Snellgrove | Published

ds9 crossover

Whether you love it or hate it, Star Trek’s Mirror Universe has been the biggest crossover connection in the franchise, linking The Original Series, Deep Space Nine, Enterprise, and Discovery together. However, there would never have been a continuation of the original “Mirror, Mirror” storyline if Star Trek writer and producer Michael Piller hadn’t been convinced that Captain Kirk made a grave error in that episode. Because Piller wanted to explore the ramifications of Kirk’s worst violation of the Prime Directive, we got decades of additional Mirror Universe stories that began with the DS9 episode “Crossover.”

No Mirror For TNG

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Star Trek: The Next Generation continued the star-spanning adventures that began with The Original Series, so many fans at the time simply assumed we’d get a Mirror Universe episode featuring Captain Picard and his crew. This would have made sense considering how much TOS influenced TNG, including Dr. McCoy making a cameo in “Encounter At Farpoint” and the episode “The Naked Now” being a direct sequel to the earlier episode “The Naked Time.” However, Michael Piller (who took over as head of the writing staff in season three) later clarified that he received plenty of Mirror Universe pitches but none that impressed him.


That changed with the DS9 episode appropriately titled “Crossover,” which had Major Kira and Dr. Bashir accidentally ending up in a Mirror Universe very different from the one that Captain Kirk visited. At the end of The Original Series episode “Mirror, Mirror,” our Kirk encourages Mirror Spock (the one with that iconic goatee) to do his best to overthrow the Terran Empire (basically, Mirror Starfleet). He was successful and Spock (who eventually controlled the Empire) encouraged peaceful reforms, but as Kira and Bashir discover, this weakened the Empire enough that it was eventually conquered by the Klingon-Cardassian Alliance.

Kirk Unintentionally Made Things Get Worse In The Mirror Universe

The idea that Kirk could have actually wrecked so much of this universe despite his best intentions is what got Michael Piller to greenlight the DS9 episode “Crossover.” He’d later say that he “couldn’t escape the idea that Kirk’s influence in the world that he left might have been profound and changed history.” It’s certainly a powerful idea: Kirk had the same criticisms of the fascist Terran Empire that audiences had and did his best to campaign for peace, and this later episode explored the long-term ramifications of the fact that Kirk hadn’t necessarily thought everything through when he made his emotional plea to Mirror Spock.

Another thing that fascinated Piller about the DS9 “Crossover” pitch is the idea that Kirk’s actions amounted to a major breach of his most important duty. Regarding Kirk trying to cause such major changes in a different universe, Piller rhetorically asked “What would be more of a gross violation of the Prime Directive?” For longtime fans of William Shatner’s Kirk, it’s also a sobering illustration that the take-charge captain wasn’t always right when he threw all caution to the wind and played by his own rules.

Fortunately, the DS9 “Crossover” episode was such a hit with fans that it led to four more Deep Space Nine episodes featuring the Mirror Universe. Later, we got the excellent Enterprise two-part episode “In a Mirror Darkly,” which didn’t feature any of our characters crossing over but did retroactively confirm the fan theory that the original USS Defiant from Kirk’s time had, indeed, crossed into the Mirror Universe when falling through a rift in space. Most recently, Discovery had an entertaining Mirror Universe arc in season one and a season three two-parter that gave a seeming farewell to Emperor Georgiou.

Crossover Made The Mirror Universe Great Again

ds9 crossover

Everyone’s warp mileage may vary, but I have immensely enjoyed the Mirror Universe adventures of these various Star Trek shows, and I felt that Discovery’s trip to the dark side was actually the highlight of the series (not counting the introduction of Captain Pike and his perfect hair). But we wouldn’t have had anything after “Mirror, Mirror” if the DS9 “Crossover” episode hadn’t confirmed how badly Captain Kirk screwed things up. Sorry, Jim: it turns out interfering in the affairs of an entire dimension isn’t as easy as putting in a cheat code and beating the Kobayashi Maru scenario.

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