Star Trek: 12 Best Alternate Reality Episodes

In the great sprawling universe of Star Trek, Gene Roddenberry introduced us to the notion of alternate realities and parallel universes early on in the second season of The Original Series. A simple transporter accident and we saw what could be and what shouldn't be, all summed up in the most perfect goatee in cinematic history.

This would not be the last time that, as an audience, we were treated to a what if? One of the most fun things to do in science fiction is to take what is familiar and flip it upside down, playing with expectation and, in honesty, giving the actors something new to do!

Thankfully this is a trope that is not confined to the mirror universe and beyond. There are many examples throughout the franchise of 'what if' episodes, shows where the characters are pulled out of what is established and then dropped into a situation that challenges them. It is one of the best ways to keep a science fiction show from going stale.

While not every time that this happens is a success, and even some of the stronger arcs would face an amount of fatigue by the time they came to a close, the episodes on this list represent a strong selection of what makes alternate reality episodes enjoyable on Star Trek.

And then the Mirror Universe was back, back, back again! Finally, Jonathan Frakes' tease to the fandom was confirmed and the USS Discovery, along with her crew, found themselves flung into the mirror universe by Stamets and the spore drive.

This is the episode in which the first season of Discovery began to find its feet. With the tone as varied as it was throughout that first year, this was a threat that the crew could come together to overcome. Plus, like in any other episode about the mirror universe, seeing the regular characters flipped on their heads is always a treat.

Captain Killy.

If nothing else in the episode was watchable, that alone made it worth the time. Sylvia Tilly may be a marmite character in the show, yet her turn as the evil commander of the Discovery was a genuine delight of the season. Less of a delighted was the continued 'Ash is clearly Voq but we just haven't confirmed it yet' drama, coming to a head in the very controversial decision to kill Dr. Hugh Culber.

This episode serves as a sequel to Enterprise's In A Mirror, Darkly. It mentions the USS Defiant, the Constitution Class ship transported over to their side by the Tholians. It may be a tangental sequel, yet serves to offer a bit of continuity that had felt somewhat lacking. It may not be as fun an episode as some of the other trips to the other side, yet it was the beginning of a step up for Discovery.