- Story by Katie Cook, Drawn by Andy Price, Coloring by Heather Breckel
The Mane 6 are summoned to Canterlot by Princess Luna, who reveals Princess Celestia has been missing for a week and Luna has been masking her disappearance since. Luna reveals she saw Celestia step into a magic mirror not unlike the one Twilight used (from My Little Pony: Equestria Girls), but cannot figure out its magic. She tasks the Mane 6 to find Star Swirl the Bearded's personal library deep below Canterlot, where she remembers that Celestia had spent much of her time learning from him in her youth, while she and Spike maintain order in Equestria.
The girls find the laboratory and start studying his notes. They learn that hundreds of years ago, Celestia and Star Swirl had discovered the mirror could be opened onto countless dimensions, and together they enjoyed studying the other parallel worlds, even bringing some of the technology advancements back for study in Equestria. One world Celestia became attached to, but Star Swirl expressly forbade her from visiting it or "him" again, and cast a spell to prevent Celestia from opening the mirror. Armed with this information, the Mane 6 return to Canterlot. Just as they try to work out how to follow her, a battered Celestia jumps out of the mirror and falls unconscious, the image of King Sombra briefly appearing before the portal closes.
As the others help Celestia tend to her wounds, she explains that in that universe, King Sombra is both her ally and a close friend, and Sombra needs the help of the Mane 6 (and Spike) and the Elements of Harmony to protect his kingdom there. Twilight gets a quick briefing on how to reactivate the portal from the other side and to use Spike for relaying messages to Celestia, and the Mane 6 and Spike step through, finding themselves in a version of Canterlot that has seen much better days. Though briefly captured by Sombra's guards due to mistaking the group for the alternate universe's version of them, they find themselves face to face with a very sane, sensible, and gentlecolt-ly (and rather dashing) Sombra, who thanks them for coming and apologizes for the guards. Before he can explain the situation, the alternate versions of Celestia and Luna arrive - Sombra's tormentors. The mares start to get into a fight with the two evil alicorns, but suddenly Spike coughs up a scroll and Sombra uses a force field to separate the Mane 6. The scroll, from the good Celestia, reveals that any damage done to the evil versions of Celestia and Luna will also harm the good versions, a side effect from the length of time that Celestia had spent in this universe that created a possible paradox according to Star Swirl's notes. As the evil alicorns fly off in laughter, Sombra reveals that he and the good Celestia love one another, shocking the others.
The good Sombra explains that Celestia and Star Swirl visited him long agonote via the mirror. Both Sombra and Star Swirl were fascinated with the other's world while Sombra and Celesta fell in love at first sight. Sombra and, at the time, a kind Luna, helped to show their visitors around and provided them with goods to take back, extending the offer for them to visit any time they can in the future. Though they would continue their visits, with Sombra and Celestia's love growing, Star Swirl discovered that their two world started to become too interconnected, and limited Celestia's visits to it more and more. Eventually, this led to Star Swirl forbidding Celestia from using the mirror as previously seen, and creating an irreparable rift between Celestia and Star Swirl. Undaunted, Celestia would look for a way to break the spell on the mirror behind Star Swirl's back.
Sombra then explains that he knows the evil version of Celestia has been trying to acquire the magic to to open the mirror from his side, offering Sombra a deal to banish the good Celestia to Sombra's world so they can be together and would leave that world at peace. Sombra has refused, not wishing the fate of his world on the main one. Twilight suggests that the same way they were able to stop their version of Sombra, with crystals, would work similarly well against the two evil sisters. The Mane 6 and Spike make plans to travel to the Castle of the Two Sisters to implement their idea, unaware that evil Luna has overheard everything to prepare her sister for the oncoming battle.
As Sombra and the Mane 7 travel to Evil Celestia's castle they notice the sky becoming ominous, a sign of the weakening of the paradox between the two worlds. When they reach the castle, Evil Celestia begins her second plan - she turns on her own sister and blasts her with full force, knowing full well this will cause the same physical harm to Luna in the prime world and assure Celestia will be by her side. Luna is thrown at the magic mirror, shattering it and causing the barriers between the two worlds to merge, bringing the good versions of Celestia and Luna to this world. Good Celestia refuses to allow her evil self to continue this and begins to use the full force of her magic to fight her. The distraction allows the Mane 6 to trap the two in separate bubbles, and for Sombra to start to encase the evil Celestia in a crystal shell; the realize too late that this is also doing the same to Celestia.
Good Celestia insists that Sombra and the Mane 6 continue the spell, but Sombra refuses to let this end. Realizing that he must restore balance between the two worlds and knowing the fate of his alternate self, he takes the power of the Elements of Harmony and uses that to drain Evil Celestia and Luna of their dark ways and absorbs it himself, taking on the appearance of the villainous King Sombra, bringing the balance from the prime world to this one. With the Celestias released from the shells, prime Celestia spends a brief farewell with Sombra before he loses his rational side and flies off. The walls of realities between the two universe begins to repair itself, with the formerly evil Celestia and Luna back to their good selves and ruling over a much kinder world. A portal opens long enough for the Mane 7 and the Princesses to escape back to their world. Back in prime Equestria, the Mane 7 help Celestia to clean up the broken mirror, Celestia keeping one piece of it to remember her Sombra by.
These issues contain examples of:
- Act of True Love: When Mirror Sombra realizes that Celestia will be trapped if they go through with the current plan for dealing with her evil counterpart, he decides on another option — absorbing the evil of her counterpart and Mirror Luna, turning himself into a similar version to the regular Sombra.
- As per the norm, Twilight is giddy with excitement when Starswirl the Bearded is even mentioned.
- Celestia of all ponies had shades of this in her younger years. In the 3rd issue (#19), we see Good Sombra, Celestia and Star Swirl having their first formal discussion over coffee after their first crossing. Celestia is so startled when Sombra compliments her on her beauty, she does an epic Spit Take into Sombra's face. Cue the next panel where Celestia realizes what a doofus she made of herself and does a facehoof.
- Advertised Extra: Despite getting a full cover devoted to them, the alternate counterparts of the Mane Six only make brief cameos in the actual story. Katie Cook's 2 page short in issue #20 lampshades this point.
- Alternate Universe: The various universes that Star Swirl and Celestia travel to via the mirror, which appear to be a mix of Another Dimension and Alternate History. For example, one appears to be a case where dinosaurs did not die out (given that the one dinosaur they see is colored like Fluttershy and has her cutie mark), while others are other variants. And then still remains the hinted Mirror Universe suggested by the future covers...
- Arson, Murder, and Jaywalking: The 2-page short in Issue 20, with the mirror Mane 6, had a wanted poster with all of them plus Spike, for a long list of "crimes". Their crimes range from vandalism, smuggling and forgery, to not eating their vegetables, taking tags off mattresses, and jaywalking.
- As You Know: Issue 18 has Celestia recap everything we learned the previous issue.
- Barrier Warrior: Mirror Sombra mentions that his magical abilities, like Shining Armor's, are mostly defensive in nature, and can keep even Mirror Celestia and Luna at bay with his force fields.
- Big Good: The Mirror Universe King Sombra. Celestia has described him as the king of that Equestria and a kind and wonderful ruler of his ponies.
- Big "NO!": Main Celestia when Mirror Sombra takes the evil of Mirror Celestia and Luna into himself to restore the balance between their worlds, turning them good while apparently making himself evil. You can even see her heart breaking inside the "O".
- Bittersweet Ending: The group manage stop the Evil Celestia and Luna and save their respective universes, apparently restoring the alternate Equestria in the process. But Mirror Sombra has to absorb the sisters' evil to do so and become the Sombra we know from the main verse. What's more the portal mirror was broken, meaning Prime Celestia will likely never see him again. The fate of the mirror Equestria is left ambiguous as it now doesn't have a ruler.
- Breaking the Fourth Wall:
- Pinkie makes a very good point about their world.Twilight Sparkle: But...But what if this [Mirror] world doesn't make 100% sense?! I need to record it all for posterity!
Pinkie Pie: Our world doesn't even make sense! Why should this one? Who needs continuity?
- If you look closely at the pieces of paper hanging on the wall on the very same panel, among them you can find a note saying "if you're reading this, you may be overthinking this comic book...".
- Pinkie does it again after Evil Celestia attacks Evil Luna in order to force Good Celestia to her version of Equestria.Pinkie Pie: You can't do that! This is a kid's comic!
- Pinkie makes a very good point about their world.
- Brick Joke: All those jokes about Twilight and her thesaurus in Issue #17 nod to when Pinkie pulls out "Twilight's Thesaurus" in issue #18 to find another way to address King Sombra.
- In the first issue, Pinkie's shown to have found chewing gum under her chair when they meet with Luna. Three issue later, Pinkie's blowing bubble gum at the height of the epic fight.
- Broken Pedestal: When they return to Canterlot, Celestia worries that she had begun this to Twilight after seeing what her actions caused. Twilight reassures her that it proved that Celestia isn't perfect and that she doesn't have to worry about being perfect either.
- Bullying the Dragon: When meeting Twilight Sparkle for the first time, Mirror Luna mocks her by patting her horn and asking "What kind of magic are you going to do with that, small one? A card trick?". Twilight zaps her in response.
- The Cameo: The Observer pony makes yet another appearance, but this time he speaks directly to Twilight. Numerous other characters show up briefly as well.
- Chronic Backstabbing Disorder: Mirror Sombra is wise about Mirror Celestia possessing this trait, knowing that if he takes her up on her "deal" and lets her into the main Equestria to conquer it so he and Main Celestia can be together in his version of Equestria, she wouldn't hold up her end of the deal, and would try and control both worlds. She later betrays and attacks Mirror Luna in order to try and lure Main Celestia to her world.
- Cliffhanger: #17 ends with a battered Princess Celestia returning from whatever universe she visited, only to immediately collapse as King Sombra looks about to emerge through the mirror.
- Continuity Nod:
- The magic mirror featured in this episode is shown to be the prototype of the one that is the focus of My Little Pony: Equestria Girls. A primary difference is that the prototype can access numerous worlds, and can be opened at any time.
- Several facets of Equestria Girls are brought up; Spike recounts turning into a dog, and Celestia comments that Sunset Shimmer has decided to live her life in the human world.
- Other elements about the function of the mirror come into play. In Equestria Girls, Celestia fears sending over more than just Twilight for fear of upsetting the balance of both universes; in #18, Celestia learns that her having spent too much time in the Good Sombra universe has caused the balance to become upset so that damage dealt to Evil Celestia is felt by the Good Celestia. Both here and in Equestria Girls, the mirrors opens on the other universe at a base of a statue.
- Luna comments that it's a wonderful night not to be banished to the moon.
- Several elements of the Luna micro comic (also created by Cook/Price) reappear, including Celestia's advisor, Kibitz, and Luna's pet possum Tiberius. Luna is shown being able to handle the responsibilities of running Equestria for 7 days straight, using lessons she likely learned from the one-off time from the micro story. Her last line in issue #17 comments on being able to handle the stress. Later, in #18 when Celestia and Luna talk after the Mane 6 leave, Luna can be seen ravaging some cake, again calling back to her Micro.
- Spike wins a game of "Monopony" against Luna and expresses his love for the game.
- King Sombra — or at least a mirror universe version of him — returns.
- Pinkie has pulled out another cake - with icing that reads "Glad You Aren't Mangled Or Anything" - out of nowhere, as she's done before in the comics.
- Spike and Angel are back in their vaudeville outfits used in the main series before.
- This occurs before the season 4 opener, since the Mane Six still have the Elements of Harmony.
- Events "over there" only recently got out of hand when that Luna was converted to the evil Celestia's ways, which Sombra states happened at the same time that our Luna was freed from being Nightmare Moon.
- Evil Celestia has an Evil Philomena, and Evil Luna has an Evil Tiberus.
- A sign on the "over there" version of Ponyville has the "F+W" logo used since the introduction of Flax Seed and Wheat Grass from the Rarity's micro - except instead of being hippies, they are now attorneys.
- As Sombra describes how he first met our Celestia he notes that this was before any of the Mane 6 were born; Pinkie questions "even Fluttershy?", referring back to the fact Fluttershy is a year older than Pinkie.
- The first time that Celestia and Star Swirl cross to Good King Sombra's universe is set sometime before the evil version of Sombra was known about in the main world. It was also sometime before Luna turned into Nightmare Moon.
- Celestia has a guard wearing an ancient-Egyptian-esque version of the main universe's armor.
- The guards in the alternate Canterlot resemble the guards Evil Sombra had in the main universe, as seen in the flashback in Twilight and Shining Armor's issue of My Little Pony Friends Forever.
- Good Luna and Celestia pass under a picture of Evil Sombra's defeat as they talk.
- In flashback, we see Star Swirl leaving to Fillydelphia to handle a parasprite problem, with a wagon loaded with instruments - as Pinkie showed to be the solution in "Swarm of the Century".
- In this same flashback, Celestia is in her library, and shows one book named after Clover the Clever, and a second book that alludes to how Clover was a student of Star Swirl, or as the title puts it "crazy unicorn wizard".
- Good Sombra and the Mane 7 debate how to stop the evil Celestia and Luna, postulating what defeated Sombra in their world would help here. Rainbow Dash, unhelpfully, brings up stairs, while Twilight nails the answer about crystals.
- Twilight's doubts about being a princess show up again.
- Chrysalis can be seen when the worlds merge where she's using the animated Pinkie costume as a punching bag.
- After Mirror Sombra absorbs Mirror Celestia and Luna's evil in order to restore the balance and save both versions of Equestria, he gains the curved horn and red eyes of his main-verse counterpart.
- The magic mirror featured in this episode is shown to be the prototype of the one that is the focus of My Little Pony: Equestria Girls. A primary difference is that the prototype can access numerous worlds, and can be opened at any time.
- Covers Always Lie: Two of the covers put together form a mirror image of the other, one showing the prime universe cast, the other the mirror universe counterparts. Most of these characters on both sides do not appear in the story.
- Crapsack World: Evil Celestia and Luna have ravaged the alternate Equestria, turning it into one of these. It actually used to be quite nice.
- Creator Cameo: On a wall in the alternate world are two wanted posters: one is for the OC of colorist Heather Breckel, while the other is a nod to Bobby Curnow, the IDW Editor overseeing the pony comics.
- Deal with the Devil: Evil Celestia tried to make a deal with Good Sombra, basically amounting to giving her the spell to go to the main Equestria, enabling her and her sister to go there while allowing Good Celestia to come to the mirror world permanently with Sombra. Sombra refused, not just because he didn't want to wish that fate on the world the good Celestia cares for, but because he's also smart enough to realize the evil princess won't stop until she controls both worlds.
- Description Cut: In a flashback, Star Swirl suggests they need a means to protect his laboratory from unwanted eyes, and considers the option of a hydra in a moat to guard the place. In the present, hundreds of years later, the ponies pass a hydra-like skeleton in the moat around the lab.
- Deus ex Machina: Lampshaded. The secret passage back to the castle from the lab helps avoid the long journey through caves to get there. Pinkie calls this trope out by name as they slide off. It's a minor example as it doesn't impact much on the plot.
- Disappointed in You: Starswirl says this of Princess Celestia once he learns she's been visiting the Mirror Universe behind his back.
- Eccentric Mentor: Luna felt that Starswirl was more like Pinkie Pie than Twilight. In general, he was very adventurous compared to Celestia, who worried about her duties to the kingdom. (Merlin from Disney's The Sword in the Stone makes for a very apt comparison).
- Everything's Better with Dinosaurs: The first universe Celestia and Star Swirl visited is inhabited by dinosaurs.
- Evil Makes You Monstrous: Absorbing Mirror Celestia and Luna's evil into himself causes Mirror Sombra to go from Tall, Dark, and Handsome to this, taking on the curved horn and eyes of the main Sombra.
- Expendable Alternate Universe: Averted, just like in My Little Pony: Equestria Girls. Twilight and co. go into the Mirror Equestria with the express intent of saving it.
- Face Palm: Celestia does this after doing a Spit Take onto the mirror Sombra after he compliments her beauty.
- FaceHeel Turn: When Celestia met Mirror Luna in Mirror Sombra's flashback, she was apparently far more happier than her own Luna. However, around the same time Nightmare Moon was defeated and Luna returned, Mirror Luna joined her evil sister.
- Potentially what happens to Mirror Sombra in the end. In order to restore balance, he uses the Elements of Harmony to transfer the evil in Mirror Celestia and Mirror Luna within himself, causing him to become just like main universe Sombra. Part of his former good self is present when he says farewell to main universe Celestia, but it's unknown what will happen to him from this point onward.
- For Your Own Good: Star Swirl seals the mirror portal because he believes Celestia's feelings for mirror King Sombra are endangering both her kingdom and his.
- Fridge Logic: In universe, the Mane Seven ask why Sombra doesn't do anything against the evil princess. Turns out that like the main world's Shining Armor, his magic is of the Barrier Warrior variety, not the offensive type.
- Twilight uses this to come up with a plan to defeat the evil princesses by sealing them in crystal, based off their battle with the main-verse version of Sombra.
- From Bad to Worse: In the final issue of "Reflections", Mirror Celestia attacks her sister in order to harm Main Luna and lure her counterpart to the alternate Equestria. But the attack causes Luna to accidentally break the mirror, causing the rift between the worlds to start causing the barrier between the two worlds to disappear entirely, and begin merging the two worlds into one.
- Fun with Subtitles: The "Meanwhile, Back at the..." boxes are a bit lemony. For example:"Back in Canterlot... Well, the other Canterlot. You know what I mean."
- Hammerspace: Pinkie produces a fairly large "Glad you aren't mangled or anything" cake and a dictionary from nowhere. Applejack tries to question this, but Rainbow Dash just tells her to go with it. Spike gets in on the action when she produces a "Welcome Home" cake at the end of the arc.
- Heroic Sacrifice: Mirror Sombra uses the Elements of Harmony to absorb Mirror Celestia and Mirror Luna's evil, restoring the balance between the worlds and causing them to have a HeelFace Turn while apparently giving him a FaceHeel Turn.
- I Did What I Had to Do: Starswirl explains to Celestia in the final flashback that he had to make the decision for Celestia, as making descions she doesn't want to make is part of being a ruler. This gets an Ironic Echo in the climax when Celestia is being encased in crystal alongside her evil alternate and appoints Twilight as the new ruler. Repeating what Starswhirl had told her.
- Ironic Echo: In a flashback, Celestia and Star Swirl, on their apparent first visit to the Good Sombra 'verse, end up in jail after Star Swirl tells one of the guards their hat is funny-looking. In the present, the Mane 6 (and Spike) end up in the same jail cell because Twilight commented to a guard that his hat looked funny.
- Irony: The stained glass windows in Sombra's castle depict some... strange paragons.
- Imagine Spot: Twilight imagines Starswirl as an alicorn at one point. This results in a Twilight laughing at the thought.
- Karma Houdini: The anti-mane six have committed quite a few crimes. ...And from the looks of things thy are going to keep committing them. The same goes for anti-Cadence, who unlike Celestia and Luna remains evil at the end of the story arc.
- Kicking Ass in All Her Finery: Evil Celestia is a clothes horse magically adopting many different evil-looking outfits in the midst of a fight.
- Leaning on the Fourth Wall: Pinkie calls out "You can't do this, this is a kids' comic!" at all the violence going on during the last issue.
- Let Us Never Speak of This Again: During the final flashback with Celestia and Starswirl, he does after accepting her apology.
- Little "No": Celestia does this - complete with a broken heart in the "O" - as Mirror Sombra absorbs the evil of his world into himself, Face Heel Turning.
- Loophole Abuse: Twilight plans to seal the evil princesses in crystal to get around the Synchronization.
- Love Makes You Dumb: The entire arc is kickstarted by Celestia's irresponsible use of the mirror despite fully knowing the huge danger it poses to her and Sombra's worlds. It ends up costing her her only friend and coming back to bite her in the ass a good thousand years later.
- Magic from Technology: Star Swirl used some of the technology they took from other universes for the basis for his magic as well as for the betterment of Equestria.
- Mirror Universe: The alternate universe visited by Celestia is ruled by the benevolent King Sombra and plagued by the evil Celestia and Luna. Discord was a superhero of some sort and it's implied the Mane 6 of that world are criminals. A set of stained glass windows show that Flim and Flam are the representation of Fairness, Princess Trixie (as an alicorn) the representation of Humility, a smart-looking Derpy with glasses as the representation of Wisdom, and a fully-whole Chrysalis as the representation of Love.
- Monochrome Past: Much of the first issue is recounting Celestia and Star Swirl's interactions in the past, as such all these pages are done in a sepia tone.
- Must Have Caffeine: Starswirl takes to coffee instantly when he first encounters it in the mirror world, and brings some back when he returns to the main Equestria.
- My Friends... and Zoidberg: Spike has to frequently remind the Mane 6, Celestia, and Luna that he's there too and willing to help in any way, whenever any of them mention the "six of them" going across.
- My Greatest Failure: Celestia acknowledges that she caused great dangers to both worlds.
- Mythology Gag:
- Luna, to disguise the absence of her sister, uses makeup to make herself look like Celestia. However, this comes out very pink - much like the initial Princess Celestia toys that started the "G4" line.
- Never Got to Say Goodbye: When Star Swirl finds out that Celestia repeatedly used the mirror in order to visit the other world's King Sombra — despite knowing of the danger it causes to balance between both universes — he promptly shuts the portal down, ignoring her teary-eyed pleas to "at least let [her] say goodbye". Later defied by Celestia, who uses her own magic and knowledge to re-open the portal behind Star Swirl's back and meet her lover once more.
- Played straight again in story arc's conclusion when Mirror Sombra brings back the balance by absorbing the evil corrupting Mirror Celestia and Mirror Luna, turning evil himself and flees without giving Main Celestia any chance to talk to him again. Since she and other heroes are forced to make a hasty retreat to their home dimension when barrier between the worlds is being restored and the mirror which served as a portal was destroyed earlier, this is definitely the last time they saw each other.
- Noodle Incident: Pinkie Pie mention a number of times Pinkie's failed at something, including a time when Pinkie tried frosting a cake while going over a waterfall.
- Not Helping Your Case: Pinkie and Fluttershy mentioning all the times Pinkie's failed at doing something doesn't help improve the mood at all.
- Never Say "Die": Pinkie Pie says that the hydra is "pining for the fjords".
- Nice Hat:
- The palace guards in the alternate universe wear helmets which look like Sombra's hairdo. Both Twilight and Starswirl find them funny, which then and now the guards do not appreciate.
- Post-HeelFace Turn, Mirror Celestia sports an Egyptian Headdress most likely to contrast with Mirror Luna Greco-Roman dress.
- Off-Model: For some reason, this arc had Spike being drawn much fatter, almost two heads taller and unlike his TV counterpart, having long, phrensile feet. At one point he is even described as chubby, showing that this was apparently intentional.
- Playing with Fire: Celestia's Super Mode has her engulfed in fire.
- Please Wake Up: Luna says this to Celestia, in a rather heartbreaking fashion when her sister returns through the mirror and collapses.
- Portal Slam: Starswirl closes the magic mirror after he catches Celestia using it without his knowledge. Celestia herself seems to do this at the beginning of #17 to ensure nopony can follow her through the mirror. The mirror breaks in #20, seemingly cutting off the two versions of Equestria forever.
- Product Placement: Princess Luna and Spike are shown playing Scrabble, Mouse Trap, and Monopoly on three separate occasions. All three are Hasbro properties. note There is also a MLP:FIM version of Monopoly.
- Reality Bleed: The rift gets even worse after the mirror breaks, to the point that the worlds start merging into one as the barrier between them breaks down.
- Reality Ensues: It's all well and good to get a giant monster to guard your lair, but they tend to die if not regularly fed.
- Red and Black and Evil All Over: Mirror Luna's choice of garments. Rarity is not impressed by this.Rarity: Red and black?! You call that original?
- Remembered I Could Fly: In taking the shortcut back from Star Swirl's lab to the castle, all but Rainbow Dash are subjected to a series of slides and other wacky devices; Rainbow simply flies following the others back with far less hazard, later commenting to Fluttershy that she could have flown too.
- Replacement Goldfish: Luna accuses Celestia of using Mirror Luna to replace her after she was sealed away, though Celestia denies it.
- Running Gag: Spike reminding everyone that he's part of the team."You six..."
- Save Both Worlds: The Mane Seven have to not only save the alternate Equestria from Mirror Celestia and Luna, but their Equestria as well, for the evil Alicorn has her sights on it...
- Sealed Evil in a Can: Twilight's plan to deal with the evil princesses is to seal them in crystal, stopping them from causing trouble while getting around the Synchronization problem. Would've worked (which Mirror Luna even admits) if Mirror Luna hadn't overheard them and tipped off Mirror Celestia who forces Prime Celestia to come to their dimension where the Synchronization is much stronger.
- Sesquipedalian Loquaciousness: Some of the signs below Canterlot Castle. For example, "Besom Repository" is 'fancy' for "Broom Closet". Twilight of course has no problem, mentioning her joy of reading a thesaurus straight through for fun. Later played up when Spike asks about Luna in her odd speaking mannerisms.
- Shoot the Shaggy Dog: Pretty much how Prime Celestia and Mirror Sombra's relationship ends — he makes a Heroic Sacrifice (which, due to the What Happened to the Mouse?-ridden ending, may or may not be Senseless in the long run), they Never Got to Say Goodbye, and she ultimately decides to Let Us Never Speak of This Again.
- Shout-Out: When the heroes are arrested, their cell has graffiti. One reads, "It wasn't me! It was the one-armed pony!"
- So Proud of You: Unsurprisingly, spoken verbatim by Celestia to Twilight in what she believes at the moment is the last time they see each other. As her mirror counterpart is being sealed in crystal — which causes her to be sealed as well — Celestia accepts her fate as a necessary sacrifice. When she's bidding final farewell to Twilight and entrusting Equestria to her (and Luna's) care, she takes time to tell how proud she is of her.
- Star-Crossed Lovers: Celestia and Mirror King Sombra.
- Stone Wall: Defensively, Mirror Sombra is practically a One-Man Army, which is why the Mirror Sisters have previously been unable to make much headway against him. Offensively... not so much, which is why he can't Just Eat Gilligan against them.
- Super Mode: Celestia's mane and tail are ablaze as part of hers.
- Super OCD: Starswirl seems to have had shades of this.Twilight: I don't understand why Princess Luna thought finding things down here was complicated. Everything is so well labeled! It's like...
Fluttershy: ...Like you built it?
Twilight: Well, yes!
- Twilight sees Good Sombra's wall of details distinguishing the two universes, and is on the verge of a Madness Makeover to document it all.
- Synchronization: Thanks to their repeated trips to the Alternate Universe, the two are now intertwined, each a reflection of the other.
- The beings in each world act completely contrary to their other selves, which even seems to update in real-time, since Alternate Luna was good until Main Luna stopped being evil.
- Celestia and Luna are directly linked to their counterparts, feeling any damage the others take. Twilight plans to get around this by using the Elements to imprison the evil princesses in crystal.
- Even minor things like choices of meal or books taken from a shelf reflect onto the other world.
- After the mirror breaks due to Mirror Celestia attacking her sister in order to lure Good Celestia to her Equestria, the Synchronization gets taken Up to Eleven, with the barrier between the worlds starting to break down entirely.
- Tall, Dark, and Handsome: Mirror Universe King Sombra, who even Fluttershy finds rather attractive.
- Team Killer: Evil Celestia seriously injures evil Luna in order to do the same to the good Luna, and this force Celestia into the mirror world to confront her evil twin.
- Tempting Fate:Rainbow Dash: I hope there aren't any monsters in here.
Applejack: Why would you say that? That is inviting that type of stuff to happen!
- It turns out there is a monster... but it's dead. That's what happens when no one is around to feed it.
- Twilight wonders how they're going to get out of a jail cell, to which Pinkie silently whacks her horn.
- Tyrannosaurus rex: Celestia and Star Swirl briefly encountered one. With Fluttershy's coloring and cutie-mark.
- Waking Non Sequitur: Main Luna gets knocked out when Mirror Celestia turns on her sister in parallel universe. When she regains consciousness, the first thing she has to say is "I don't want a cutie mark in accounting... I want to be the moon...".
- What the Hell, Hero?: Star Swirl is very disappointed when he finds out Celestia has been visiting the Mirror Universe behind his back when he made it very clear that frequent visits might cause problems for both worlds.
- Luna isn't pleased either when Celestia confesses she used Mirror Luna as a replacement for her real sister.
- Wham Line: The Mane 6's (and Spike's) reaction to this tell it all.King Sombra: Does [the message] say anything else? Does it say if Celestia's okay? My dear, sweet Celestia, I need to know!
Pinkie Pie: ...Your...
Twilight Sparkle: ...Celestia?
- What Happened to the Mouse?: In the end of the arc, Celestia and Luna get turned good at the end... But Mirror World Cadence is still evil and still out there. What's going to happen to her?