On October 6, 1967, the Star Trek: The Original Series episode "Mirror, Mirror" showed us a parallel world with an Empire instead of a Starfleet and United Federation of Planets. It was a place the franchise would return to in five episodes of Deep Space Nine and a two-parter on Enterprise.
As the years went by and the franchise changed, we saw the mirror world evolve, as well as more characters come face-to-face with their mirror selves, who, for the most part, were very different. Like Captain Kirk before them, our favorite characters often intervened in the mirror universe's affairs, leading to changes we'd only discover in future episodes.
However, while some of the episodes that followed "Mirror, Mirror" made for fun, interesting additions to the idea of the mirror universe, others lacked the same creativity and did not take full advantage of the world's potential.
Looking at all these, here's how I would rank Star Trek’s mirror universe episodes, from worst to best.
“Resurrection," Deep Space Nine Season 6
This episode starts with the mirror universe's Bareil Antos transporting right into ops and trying to take Kira hostage to escape the station. When he fails, he convinces Kira he was just trying to escape the Alliance and doesn't want to go back to the other world. Speaking with him makes things confusing for Kira, considering she was in a relationship with his counterpart before he died, and it's something Sisko tries to talk to her about since he was in a similar situation when he met the mirror version of his wife Jennifer.
Kira ends up getting much closer to this mirror visitor after he joins her for dinner with Dax and Worf, and it’s a shock when she realizes he's there to steal the Orb of Prophecy and Change as part of a plan with her mirror self, Intendant Kira. However, quite predictably, Bareil can't go through with it and after telling Kira it would never work between them, he returns to the mirror universe with the Intendant.
"Resurrection" is the least interesting of these episodes. With Bareil they're repeating the same ground they did with Sisko and Jennifer in earlier episodes, only in this one Kira lets herself get very close to him. I also never felt Bareil was a particularly great character or that he had good chemistry with Kira, so bringing him back even as a mirror version just doesn't make for a compelling story.
Best scene: Dax and Worf host dinner
The best parts of this episode were the fun friendship moments between the characters, such as when Dax, Worf and Bashir are waiting for Kira hoping to hear about how her night with Bareil went. Topping that to become the best scene is the dinner between Dax, Worf, Kira and Bariel. I love the idea of Dax and Worf hosting dinners as a couple, and the scene is both sweet in how it shows the characters' connections and funny thanks to Worf's reaction to Bariel's story ... and how he's ultimately being proven wrong!
"The Emperor's New Cloak," Deep Space Nine Season 7
The last mirror universe episode of Deep Space Nine finds Quark and Rom trying to save Grand Nagus Zek, who traveled there to see about business opportunities and ended up a prisoner of the Alliance. Quark needs to bring a cloaking device in exchange for Zek's release and he recruits Rom to help. They go with mirror Ezri to make sure the Regent will release Zek but end up being caught by the rebellion and find themselves rescued by a nicer Brunt.
After bringing Worf the device, he throws the Ferengi in a cell with Zek until they need Rom's help setting it up. Intendant Kira and Garak are also there causing problems, leading to some hilarious scenes where the Ferengi tell mirror Garak about their Garak to confuse him and delay Garak in killing them. They're able to eventually escape and go home as the rebellion captures the Regent, meaning there might be even bigger changes in the mirror universe if anyone was to visit again in the future!
Like most of the episodes featuring Rom and Quark, "The Emperor's New Cloak" is entertaining thanks to some humorous moments, and it's fun to see their reactions to things in the mirror universe. However, new characters such as Ezri, Brunt and even a human Vic Fontaine aren't very interesting and overall the plot is predictable.
Best moment: Rom constantly confused by the mirror universe
Throughout the episode it's hilarious how Rom consistently confuses himself as he thinks too hard about the alternate universe. This first happens when the rebellion captures him and Quark and they meet Smiley, who Rom thinks is just as nice as their O'Brien ... but how does that make sense if everything is alternate? He then gets very confused by Brunt being nice and their food not being poisoned. Then when he tries to think about their Ezri not betraying them, but this one betraying them, Quark just asks him not to start again. Like Rom says at one point, it's all very confusing …
"In a Mirror, Darkly," Enterprise Season 4
Enterprise's two-part episode "In a Mirror, Darkly" was set entirely in the parallel universe with only the U.S.S. Defiant and her dead crew from The Original Series episode "The Tholian Web" crossing over.
The episode starts by showing us the differences in the history of the mirror universe that led to the Empire, including Zephram Cochrane shooting the Vulcans that visit Earth for first contact instead of greeting them peacefully. Here we find the Enterprise is part of the Empire with Maxwell Forrest as captain and Archer as first officer. Instead of following their orders, Archer wants to head to the Tholian system to investigate something he thinks can turn the tide against the rebels currently standing up to the Empire.
This leads to Archer leading a coup against Forrest and taking command, ultimately making it so that even when Forrest is able to retake the ship with T'Pol's help they cannot change course. Archer explains how the Tholians created a doorway to another universe and lured the ship, which is also from 100 years in the future. Archer and a boarding party head to the Defiant while the Tholians destroy the Enterprise, leading to everyone who survives boarding the more powerful starship.
Archer wants to use the Defiant to take control of the Empire and becomes paranoid. He starts to take out the leadership and stops Vulcans and other non-humans on board who were inspired to rebel when learning about the Federation in the other universe. After Archer orders all that information deleted, Hoshi Sato poisons him, takes command and arrives on Earth, proclaiming herself Empress.
These events set before "Mirror, Mirror" are quite original. From little details like revealing the mirror universe's early history and the development of the familiar Agony Booth to nostalgic callbacks like The Original Series uniforms appearing on the Defiant and Archer fighting a Gorn, these elements helped make "In a Mirror, Darkly" at least a unique mirror universe episode that stands out from the others.
Best scene: The opening credits
One of the most impressive things about this two-parter was how the show changed its opening credits to fit with the mirror universe. The images shown were of those set in the mirror universe's history instead of the regular universe and the music was also different (and considerably more menacing).
"Shattered Mirror," Deep Space Nine Season 4
Mirror Jennifer makes her final appearance in the third mirror universe episode of Deep Space Nine and this time she meets Jake. Jennifer crosses over under the pretense of wanting to tell Sisko the rebellion has taken Terok Nor. She ends up spending time with Jake when Sisko has to go to a meeting and, unfortunately, when left alone, Jennifer takes Jake back to the mirror universe.
Sisko follows to get him back and it turns out it was all a plan to get Sisko's help in completing their own Defiant before the Alliance fleet shows up at the station. Sisko helps in order to get him and his son back home, but in the meantime Jake becomes quite attached to Jennifer since she reminds him of his mother. It all leads to a bit of an emotional rollercoaster as Sisko helps them get the Defiant working and the fleet retreats, but Jennifer dies when Intendant Kira tries to shoot Jake and she jumps in the way.
While it's interesting to see Jake's youthful curiosity react to the mirror universe, it's sad to see him and Sisko going through so much with Jennifer. It's also clearly a lot for her to deal with as well. However, it feels a bit like ground that was already covered in the last episode, even though Jake adds a new dynamic, and the episode is not as exciting as the others as a result.
It's fun to see new characters like Nog and Worf in the mirror universe, but it feels like this episode brought them all together just to make Sisko and Jake relive the pain of losing Jennifer again.
Best scene: Worf and Garak arguing about a key
At least in this episode there were some absolutely ridiculous and weird moments thanks to Worf and Garak, the best of which is a scene about a lost key that really has no point other than to show how crazy this universe is. Captured after escaping Terok Nor, Garak is now a prisoner of Regent Worf, complete with a collar around his neck connected to a chain held by the Regent. At some point a Klingon claims Garak stole the key to his chains while the Klingon was feeding him. Garak says he didn't do it but Worf doesn't believe him, even though they searched him and didn't find it. Worf throws him around and eventually accuses him of swallowing it. He stabs Garak in the stomach but then Worf finds the key, which apparently fell into his boot.
The whole thing is crazy, but then again, this is the mirror universe …
"Through the Looking Glass," Deep Space Nine Season 3
In Deep Space Nine's second mirror universe episode, it's Commander Sisko who gets to cross over thanks to that world's Miles 'Smiley' O'Brien paying a visit and forcing him to go. Once on the other side, Sisko turns the tables on Smiley, who explains what's been happening since Kira and Bashir visited in the first mirror episode "Crossover." There's a rebellion going on against the Klingon Cardassian Alliance and Mirror Sisko was leading it until he was killed. Now they need someone to complete his mission, which was convincing his wife Jennifer, a scientist helping the Alliance, to help the rebellion instead.
Not wanting the rebellion to be forced to kill her, Sisko agrees to help convince her to switch sides and assumes the role of his mirror counterpart to convince everyone that Mirror Sisko never died. As he meets with the fellow rebels and goes to Terok Nor for Jennifer, we meet new mirror characters like Bashir, Dax and Rom as well as familiar ones from the previous episode such as Intendant Kira and Garak (there's even an in-universe crossover appearance by Tuvok!).
While things get complicated once Kira and Garak learn about their plans, Jennifer joins the rebellion thanks to Sisko, who is returned to his universe by Smiley.
It's fun to see new versions of characters and how things have been impacted since the first Deep Space Nine mirror episode, but other than the fact that it's great to see Avery Brooks play a very different Sisko, it's still not the best Deep Space Nine mirror episode. He's really the only one in addition to the Intendant (since Nana Visitor always does an excellent job with her) that truly shines here; everyone else is kind of lackluster.
Best quote: "Why don't you start by telling me what happened to my husband?" – Jennifer
Sisko manages to fool everyone into believing he's Mirror Sisko — except for Jennifer. His actions and words that ultimately convince Jennifer to join the rebellion are enough to show her that this man is not really her husband. The episode does make it very obvious that she realizes this through some of her comments and looks she gives him in certain scenes, but it's this casually delivered line that makes for the full reveal and catches Sisko by surprise right before he leaves.
"Crossover," Deep Space Nine Season 2
"Crossover" returned Star Trek to the mirror universe on TV for the first time since The Original Series episode aired 27 years earlier. Here it's Kira and Bashir who travel to the parallel universe after having problems exiting warp in their runabout when going into the wormhole. It doesn't take long for them to realize something's wrong and soon they find themselves facing people who look like those they know on their side but who are very different here. With Kira's alternate self watching closely and Bashir stuck in the mines with a violent Odo, the two try to figure out how to escape and find a way home.
The first mirror episode of Deep Space Nine was a refreshing experience as we met the alternate versions of this series' characters. I really enjoyed the roles they gave the mirror counterparts of Kira, Odo, Sisko, O'Brien and the others, and it looked like the different parts must have been a lot of fun for the actors to play.
It was also fascinating to see how the mirror universe changed since that first visit by Kirk and the others years ago. Not only did that visit influence the political structure of the universe, it also impacted things like transporter technology, which had been redesigned so such an event could not happen again, and prompted protocols of what to do if anyone appeared from the other universe. It's great to see how that visit actually became a very important and famous event in mirror universe history.
Plus after this episode it looks like history repeats itself in a way, with Kira and Bashir leaving just as big a mark as they inspire the Terrans to stand against their oppressors. Out of all the Deep Space Nine mirror episodes, this first one is the best.
Best moment: O'Brien's speech to Intendant Kira
We had a sense that Bashir may have finally gotten through to the mirror version of O'Brien when he agreed to help if he could leave his universe behind. However, it's here when they're caught and about to die -- and Kira asks him how he could do this after all his years of service -- that we see just how much Bashir has made an impact. O'Brien gives a moving speech about how all of them might have turned out differently if history had gone ... and wherever Bashir is from, it's got to be something better than what he's living in. It's an inspiring speech that even prompts Sisko to rebel.
"Mirror, Mirror," The Original Series Season 2
The episode that started it all is still the best mirror universe episode of Star Trek.
Kirk, Scotty, McCoy and Uhura find themselves in the parallel universe thanks to a transporter malfunction when trying to return to the Enterprise after speaking with the Halkans. They notice things are different pretty quickly since their clothes have changed, everyone starts saluting and Spock appears to have grown a very sinister-looking beard! They head to sick bay, where they figure out they must be in another universe and have to find a way to get back.
These strangers in a strange land try to blend in as they come up with a plan, but Kirk's delaying the destruction of the Halkans in this universe starts to make Spock suspicious and soon it's a race against time to get back before Spock is supposed to kill Kirk and deal with the Halkans himself.
Along the way Chekov tries to assassinate Kirk and ends up in the Agony Booth, Uhura has to distract a creepy Sulu and Kirk discovers he's been considerably successful in this universe because of the Tantalus field, a piece of technology that vaporizes people.
After the four fight Sulu and Spock, they're almost able to escape with the help of Marlena before being delayed by both her and a recovered Spock. However, it turns out this Spock wants his captain back, so he's willing to let Kirk and the others go. They return to their universe ... where a beardless Spock waits for them.
While little things like the characters changing clothes with their counterparts don't make a lot of sense, this episode is otherwise amazing. While some of the 'evil' counterparts are quite stereotypical, they're also a lot of fun and let the actors play around with the characters in new ways.
Ultimately, the mirror universe with its alternate history was extremely creative ... and not a place easily forgotten.
Best scene: Kirk's speech to Spock
We know thanks to Deep Space Nine that this speech had quite an impact on Spock and did end up changing the fate of the Empire. Before leaving the mirror universe, Kirk speaks to Spock about how illogical and wasteful the Empire is, and since the Empire will fall eventually anyway Spock should change the present. He gives Spock the power to do so by leaving him the Tantalus field and leaves the Vulcan with the idea of freedom over tyranny. Spock says he will consider it ... and, as we know, he does and acts upon it, leading to many changes in the Empire. It's a great speech delivered by Kirk and one of his most memorable.
Share in the comments which mirror universe episode or moment is your favorite!