Star Trek has an ongoing motif of the Mirror Universe:

The "mirror universe" is an informal name for a parallel universe first recorded as visited by James T. Kirk and several officers from the USS Enterprise in 2267. This parallel universe coexists with the prime universe on another dimensional plane. The mirror universe was so named because many people and places seemed to be opposites of their characteristics in the prime universe, with numerous good aspects now evil and vice versa, thus "mirror"-like.

We See this in Star Trek TOS: The Alternative Factor, Mirror Mirror and The Tholian Web.

We see this in Star Trek Deep Space Nine: Crossover, Through The Looking Glass, Shattered Mirror, Resurrection, and The Emperors New Cloak.

We See this in Star Trek Enterprise: In a Mirror Darkly, and In a Mirror Darkly Part II.

My question is: Why didn't Star Trek TNG explore the mirror universe?

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    It did in a book: en.wikipedia.org/wiki/Dark_Mirror_(Star_Trek_novel), though that doesn't really answer your question
    – Nolimon
    Commented Nov 28, 2017 at 22:44
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    Voyager also did not explore the mirror universe. Which I think was a lost opportunity for the writing team to have fun with the crew, as they did in "Living Witness".
    – Xantec
    Commented Nov 28, 2017 at 22:48
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    Some of the mirror universe episodes were super-cheesy. I think that was probably part of the reason some of the series dodged it. Commented Nov 28, 2017 at 22:55
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    Riker had a goatee and they couldn't figure out another way to make him look evil.
    – Josh King
    Commented Nov 28, 2017 at 23:02
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    How are The Alternative Factor and The Tholian Web mirror universe episodes? Not all alternate universes are The Mirror Universe, and if you include them and mean to ask about alternate universes more generally, then basic research would show you a bunch of TNG alternate universe episodes like Yesterday's Enterprise.
    – J Doe
    Commented Nov 29, 2017 at 0:02

3 Answers 3


This was addressed in an interview with showrunner Brannon Braga. In short, they recognised that the mirror universe episode in TOS was a fan favourite and didn't want to make something that compared unfavourably.

However, there was a specific line they never crossed. In response to a question on why they never did a Next Generation mirror universe episode, Braga responded:

"We were a little frightened at doing it, and doing it badly, and maybe never really figured out what the Next Generation take would have been on it."

STLV17: Brannon Braga On How Kirk Should Have Died, ‘Star Trek: Enterprise’ Regrets And More

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    It's a good point really, a Mirror Universe TNG would be at best a fun retread: an evil crew working for an evil Federation. At least with DS9 their ongoing storyline gave them a cool way to change it up because the idea of the Terran empire getting defeated dovetailed perfectly with their repeated themes of rebellion/oppression with the Bajorans/Cardassians/Maquis, just changing up the sides. Commented Nov 28, 2017 at 22:52
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    Given that (in my opinion, although I know I'm not alone in feeling this way), the DS9 mirror universe stuff was terrible, it seemed that the TNG writers' fears were justified.
    – Buzz
    Commented Nov 28, 2017 at 23:30
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    @Buzz agreed, however I always felt it was just a way for the cast to have some fun and play characters that were in a different situation from their usual roles, a bit like the episode where Sisko is a Sci-Fi writer in 1950s Earth... Something we shouldn't read too much in from a main story point of view.
    – komodosp
    Commented Nov 29, 2017 at 9:24
  • There's also the fact that, in its first couple of seasons, TNG reused a lot of plot concepts and unused scripts from TOS. "The Naked Now" is a well-known and oft-panned example, and there were others. Once the show found its feet, they were probably worried about how fans would see them going back to the TOS well again.
    – Cadence
    Commented May 10, 2018 at 22:27
  • @colmde: The difference is that in 1950s Earth, the cast played different characters. In the mirror universe episode, everyone plays the same character of a murderous megalomaniac. Commented Apr 12, 2020 at 13:46

While the statement quoted in Valorum's answer certainly serves as a justification, it sounds like a quite idealized line of reasoning. In particular, the quoted text appears to have originally been published in that article in 20171, literally decades after TNG had been produced, and therefore may well be a retroactive explanation.

Instead, I'd like to suggest an additional justification:

Star Trek has an ongoing motif of the Mirror Universe:

This was very much not true during most of the time back when TNG was produced.

At that point, the only canon installment ever to touch upon the mirror universe was the TOS episode "Mirror, Mirror"2. At that time, it was a singular one-off occurrence.

Therefore, while there may have been thoughts about revisiting that universe, given that the TOS episode was fairly well-received, it's not particularly surprising this episode didn't end up with a direct sequel, like so many other TOS episodes.

As an additional reason, I'd like to point out that the mirror universe, popular as the TOS episode may or may not have been, is not an inherently viable concept when it comes to storytelling. In my opinion, virtually all sequels in DS9, ENT, and DIS are proof of that:

  • First, in general, the mirror universe episodes thrive on showing the faces of our beloved characters in a very different setting. Once that surprise is gone, there isn't much left to build upon: Virtually everyone just follows the same clichés of acting as a ruthless opportunist who will betray and kill as they see fit. Nothing anything does is relevant, anyway, anyone can be killed off at any time without any emotional impact (they're all merciless villains, anyway ...) and will be replaced with the same kind of cookie-cutter villainous character by the next occasion.
  • DS9's first foray into the mirror universe was interesting in that it showed a new situation compared to what TOS had presented. The DS9 sequels, on the other hand, were increasingly insignificant to what would happen to the real characters, and increasingly silly, with overblown (scaled-up) capital ships and designed just in some way to throw all the known characters (or rather, their actors) together.
  • ENT's sequel didn't have any relation at all to the rest of the series, and thus, again, was just a meaningless playground.
  • For DIS, with its generally darker tone, it was apparently realized that the playfulness of previous mirror universe episodes might come across as too silly. Instead, the mirror universe morphed into some overly brutal nightmare that was, IMHO, downright unbecoming of Star Trek as a whole. Ultimately, the trend that during DIS season 2, Emperor Georgiou's background was apparently more or less "forgotten" about confirms to me that the writers have no idea what to do with the purely "evil" mirror universe characters.

And on top of all that, the mirror universe doesn't make for an interesting scientific concept, either, because the idea that, in a vastly different universe, the very same people (in terms of faces and names) would be together in strangely corresponding positions (across a timespan of two centuries) seems simply too far-fetched.

Therefore, I repeat my above conclusion: While it would have been an option, there is nothing particularly surprising in the fact that TNG didn't happen to show the mirror universe.

1: Please correct me if I'm in the wrong there. Memory Alpha just links to that 2017 article for said statement, as well.

2: You mention two additional TOS episodes related to the mirror universe. However, while "The Alternative Factor" dealt with the concept of parallel (and possibly contrasting) realities, there is no reason to assume it was in any way related to the mirror universe shown on other occasions (albeit I admit, given the mess that the episode's plot is for various reasons, it is hard to make any definitive statements on what is or is not supposed to be happening throughout the episode).
The other episode, "The Tholian Web", was not related to the mirror universe at all. The episode left an open question of what became of the U.S.S. Defiant that vanished to an unknown place, but it would be a stretch to assume it was already planned back at that time that the ship had ended up in the mirror universe (and a century earlier no less), as was ultimately retconned in ENT: "In a Mirror, Darkly".

  • This feels more like a rant against the various shows that came after TNG rather than an answer with any serious research behind it
    – Valorum
    Commented Apr 12, 2020 at 14:26
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    @Valorum: Sorry if you got that impression. I'm not sure how you arrive at the conclusion I rant against shows that came after TNG. If anything, this answer expresses my disappointment with the overall concept of the mirror universe, which, IMHO, created mostly sub-par episodes in the otherwise very enjoyable shows. Also, I'm not sure what kind of "serious research" you expect exactly - I actually put quite some effort into describing in-depth what is problematic about the concept and why a sequel in TNG could not as "naturally" be expected as the question insinuates. Commented Apr 12, 2020 at 15:14

Answer is actually pretty simple… as brutal and cutthroat as the characters in the mirror universe were and with the prime universe Enterprise D being a ship full of children and families it really would not make sense that the Enterprise D would even exist in a mirror universe in the first place

  • Why not? The mirror Enterprise wouldn't have to have families, just the alternates of the main crew. This feels like a personal theory; do you have any evidence to support it?
    – DavidW
    Commented Aug 26, 2021 at 1:04
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    We saw in "Yesterday's Enterprise" a version of the Enterprise-D that clearly wasn't carrying families - Wesley being in uniform was a nice hint at how militarized the Federation was at this point.
    – user888379
    Commented Aug 26, 2021 at 1:15

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