As the show is animated primarily in a fairly old version of Adobe Flash, many Bloopers are as likely (if not more likely) to be the result of software error as they are to be the result of animator error. A scene may look perfectly normal within the program itself, but when exported to video, a layer may fail to render, or else be rendered in front of another layer that it should have been rendered behind.
A good place to see these bloopers pointed out is a fan series called "My Little Bloopers: Mistakes are FOREVER!", maintained by YouTube user WhitehawkePAUNCH.
Most animation goofs can be attributed to the fact that most characters have an asymmetrical design and the animators, rather than creating a different set for each side of said characters, merely flip it to the other side. This is also the explanation for the ponies wearing inverted number tags during "Sonic Rainboom", and why most of the ponies have reversible numbers like 8 and 11 in "Fall Weather Friends".
Characters on the show usually use "anypony" instead of "anybody," but the show slips up and uses "anybody" on occasion, even when addressing or referring to characters who aren't ponies.note This can be justified by claiming that "anybody" encompasses all species, while "anypony" refers only to other ponies, but sometimes "anybody" is said when ponies are the only intended subject of the sentence, and in "The Return of Harmony Part 1", "nopony" was used twice to deny non-pony characters. It could be that using "anypony" when it isn't technically correct is similar to calling a not entirely male group "you guys." Word of God eventually said that "The general rule was they said 'everypony' even if Spike or donkeys, etc. were in the group being addressed."
Applejack's freckles are layered above her eyelashes.
It almost seems to be a Running Gag for saddlebags to appear and disappear at random, as this happens just about every time they're used. The single most extreme example is in "Dragonshy", where everypony's saddlebags appear and disappear at random throughout the entire episode.
Each character who has freckles (e.g. Applejack and Snails) has at least one scene where one or more of their freckles vanish, only to reappear seconds later.
Applejack in particular, as her season 1 running animation (which was used a lot) had them missing.
Due to the time and difficulty of creating multiple unique ponies, any time there's a crowd scene, background ponies will be doubled. Especially noticeable with ponies like Sweetie Drops/Bon Bon that have unique mane colors.
In several crowd scenes, many—if not all—of the generic background ponies will be blank-flanked.
Though it's hard to notice, a certain aerial shot of Ponyvillenote used in "Bridle Gossip" and partially in "The Return of Harmony Part 1" contains multiple Trixies—what's more, all of them are blank flanks, even though Trixie already has a cutie mark.
Quite a few animation errors happen to Cheerilee. The most common error for her is the top of her normally two-toned mane becoming solid-colored, but (as detailed below) she's also had a different tail and sometimes cutie mark (the same as those of background Pegasus Parasol / Showers, who Cheerilee shares the upper half of her mane style with), had a missing leg, had her face disappear, and had a different eye color.
This video provides an extensive overview of most of the errors throughout the first season.
Friendship is Magic, part 1 (Mare in the Moon)
When Twilight first lands in Ponyville, Big Maintosh is shown with sparkles around his cutie mark.
When Twilight is introduced to the Apple family, Applejack shoves a green apple in Twilight's mouth. A few seconds later, she spits out the pieces of a red apple. The same scene also includes this rather bizarre◊ animation error with Twilight's eye.
Maybe her inherent magical field caused it to go ripe.
That, or her mouth bled.
Twilight's Cutie Mark is missing when she is shown after Fluttershy bumps her out of the way to talk to Spike.
Friendship is Magic, part 2 (Elements of Harmony)
There is a scene where Princess Celestia's tail is coming from her Cutie Mark rather than straight behind her.
At the closeup of Luna nuzzling Celestia, Celestia's body looks like a swan due to her hind legs having vanished.
The Ticket Master
Applejack talks about getting "these Golden Delicious in the barn by lunchtime" while she's transporting two baskets of bright red and green apples (and just possibly one yellow one on the other side that is barely visible for a moment). The number of green apples also decreases between shots.
When Twilight finds Fluttershy doing her 'spring cleaning', her wings start flapping out of sync.
During a group shot of Twilight's friends, one of Fluttershy's wings is blue.
When Rarity yells "Makeover!" and Spike flinches, his "ears" disappear.
Griffon the Brush Off
After Rainbow Dash collapses after Pinkie Pie finds her at the lake, the view switches and Dash's wings disappear.
In this same scene, every time Pinkie Pie raises her forelegs, her water wings disappear.
The circle of ink is initially around Rainbow Dash's left eye. When she looks at her reflection in the lake, the ink circle is suddenly on her right eye.
When Rainbow Dash runs and jumps off the ledge, her Cutie Mark is different—specifically, it's an old, unused design.
When all the others pile up behind Fluttershy to push her towards the cave, Rainbow Dash is second in line right after Twilight Sparkle. When they look up from behind her in the next shot, she is farthest away instead.
Towards the beginning avalanche zone segment, Fluttershy is startled by a falling leaf landing on her flank. As she screams "AVALA—!!", she is temporarily drawn with Twilight Sparkle's almond-shaped eyes instead of her usual Tareme.
Look Before You Sleep
When Applejack knocks Rarity off the bed, Rarity has an extra leg for one frame.
In the following scene, the bedsheet is missing its stripe at its top.
A tray of cupcakes spontaneously appears on the table Pinkie Pie is standing on at the end of her song about Zecora.
When Twilight says "Catchy", Pinkie Pie is standing on the table, but when she responds "It's a work in progress", she is standing on the floor without having moved.
...but then again, Pinkie has rather the history for appearing in places she shouldn't. Watch 'Green Isn't Your Color' if you don't believe me.
After Appletini puts a makeshift bridle on Rainbow Dash and attempts to ride her off, the leaf on the bridle disappears momentarily as Rainbow protests.
Right after Twilight and friends get into Zecora's place, Zecora's golden bracelets change from one arm to the other.
Twilight is seen using her magic to brush her hair... and then it is revealed her horn was limp. Perhaps the Poison Joke doesn't actually have any effect on the horn's powers, only its appearance.
Or levitation of very small objects was the only magical ability Twilight retained.
Swarm of the Century
When Spike complains that the parasprites are messing up his cleaning, the window next to him shows a night sky instead of day like all the other windows.
Rainbow Dash's goggles appear and disappear at random when Twilight's group is back at Ponyville.
Pinkie Pie's accordion moves from her right flank to the left and then returns to her right flank.
Princess Celestia's wings switch from unfurled to furled between shots.
Pinkie Pie holds the trombone completely incorrectly at the end (moving the slide with the wrong hoof and supporting the instrument from the wrong side), as well as the fact that the physics when Pinkie Pie both mimes and plays the trombone are reversed. When she sings the "Daaaauuuuuuuuu-uh!" glissando, her arm should move out then in, instead of in then out. When she plays it at the end, the pitch is rising at the beginning of each "wah!" as she moves the slide out, which is the opposite of how a trombone works. Still hilarious, though.
Winter Wrap Up
During the opening scene when Twilight goes outside only to find that she's a little bit too early for the titular wrap-up, the entire exterior shot is devoid of snow.
Joke goes that she's just THAT early.
Both Rainbow Dash's and Applejack's team armlets spontaneously swap from one foreleg to the other, or disappear entirely.
In the song, Cheerilee is missing a leg when she pulls a cart.
Call of the Cutie
During the classroom scene at the beginning, Cheerilee has Parasol's tail for two shots and the Sweetie Belle Palette Swap at the desk to Twist's left is replaced by Sweetie Belle herself for two other shots.
During the scene where Rainbow Dash is coaching Apple Bloom on getting her Cutie Mark, Rainbow Dash says "I said, are you ready?" as the camera zooms in on her face. When the camera cuts back to Apple Bloom, her ear is missing.
In the shot where Scootaloo and Sweetie Belle reveal that they don't have their Cutie Marks, the porch outside the door overlaps the floor inside the door.
Fall Weather Friends
Applejack and Rainbow Dash play horseshoes at the beginning of the episode. Rainbow has the closest horseshoe to the stake before Apple's final throw, but when the shot changes to first person, Apple's first horseshoe is closer.
Rainbow Dash is drawn without her wings when the race is about to begin.
During the race, after Rainbow Dash trips, the thundering herd of ponies that goes past includes another Rainbow Dash.
The Rainbow Dash clone is also visible mixed in with the pack when Applejack trips. Both times she's wingless and ropeless.
Suited For Success
When Rarity brings her friends in to see their (first) new dresses, she leads them to stand directly in front of her bed. A couple of shots later they're standing in front of the door, with the bed behind them on their left.
Rainbow Dash's "What?" during the song has the wrong inflection. It's done with the tone of "I didn't hear you" when it should be the tone of "What is it?"
Rainbow Dash's Cutie Mark is absent when Rarity discovers her in the tree with Opalescence.
This is not necessarily an error; what we saw very well may have been the INSIDE of her flank, in which case no Cutie Mark would be visible.
When Twilight models her dress in the second fashion show, she isn't wearing earrings, but is seen wearing them in later shots.
Feeling Pinkie Keen
When Twilight first starts spying on Pinkie Pie, Twilight's Cutie Mark is missing up until she pounces on Spike.
Twilight and Spike disappear for a split-second during Pinkie's second "twitchy tail" incident.
When all the ponies are in the library, Fluttershy switches from standing on the floor next to Rainbow Dash to standing on the stairs (but still next to her) and back again.
When Rainbow and Fluttershy are flying towards Cloudsdale, in the shot where the city is revealed, both of them have their right wings on backwards (or mirrored, since they still show the underside feathers on the underside).
Right before Rainbow suggests that she and Fluttershy could show the others around Cloudsdale, a brief shot past her from behind shows her wings folded, whereas for the rest of the scene and immediately before and afterwards they're spread.
The ponies are asked to wear white coats and white hard hats during their visit to the weather factory, but Twilight's hard hat disappears between scenes and Applejack's hard hat is replaced by her cowboy hat for no apparent reason.
Scootaloo's wings appear and disappear during the entire scene where the CMC is trying to catch Fluttershy's chickens.
In the next scene, when the girls promise not to do any more crusading for the night, Scootaloo and Sweetie Belle are animated speaking each other's lines.
When Fluttershy warns Cutie Mark Crusaders of the cockatrice, you can see her Cutie Mark on the inside of her rump, possibly due to poor copy-pasting of hindquarters in Flash.
When Fluttershy stares down the cockatrice, seen from the side, her wings are tucked, clearly frozen in stone. Seen from the front, they're open and giving her much more presence.
We could be seeing from the cockatrice's perspective. He might see the wings out when they really aren't because Fluttershy's Stare is just that intimidating.
The Cutie Mark Crusaders say lines in each others' voices quite a bit throughout the episode:
At Carousel Boutique in the beginning, Scootaloo says "Very ready" in Sweetie Belle's voice.
Later at Fluttershy's house, Scootaloo says "I'm gonna get my mark first" in Sweetie Belle's voice. Sweetie replies with "Nuh-uh" in Apple Bloom's voice.
Apple Bloom and Sweetie Belle say "Me too" and "Me three" in each other's voices.
As the Crusaders are going to bed (but not really), Scootaloo says "Yes, Fluttershy" in Apple Bloom's voice. Sweetie Belle then says "We promise, Fluttershy" and "So what kind of crusade are we going to do next?" in Scootaloo's voice.
The Show Stoppers
During the montage where the Cutie Mark Crusaders are trying to get Cutie Marks for rock-climbing, all three fillies have orange eyes. Apple Bloom's eyes are supposed to be that color, but Scootaloo's are normally purple while Sweetie Belle's are normally green.
Twilight and Cheerilee walk into the library. After Scootaloo pops up out of the pile of books, Cheerilee is suddenly wearing a pair of saddlebags.
Shortly afterward, when the Crusaders walk out of the pile, Scootaloo is missing her wings (again).
The audience at the talent competition consists, ironically enough, entirely of adult ponies with no Cutie Marks (plus Applejack).
When the Cutie Mark Crusaders are walking away from the stage, the objects in front of the back wall and parts of the back wall itself move as the camera pans across.
When Spike is telling his secret to Twilight and Pinkie Pie, Pinkie Pie's head suddenly and blatantly vanishes.
During a shot when Photo Finish is walking away from the camera, we briefly see she has Twilight Sparkle's cutie mark.explanation Ponies in this show rarely turn away from the camera (due to Hasbro mandate), especially in any direction other than straight back. But Photo Finish walks off at an unusual angle, and the animators probably used the only walk cycle of that they could find, Twilight's. They either didn't notice the visible cutie mark, or did but forgot to change it.
Over a Barrel
When we see some Appleloosans dancing their Wild West dances, the town hall can be seen damaged with a huge hole in the place of clock tower, even though the tower didn't collapse until later in the episode.
A Bird in the Hoof
Applejack can be seen wearing her cowboy hat for one brief shot during the dinner for Princess Celestia. In all other scenes from the dinner, Applejack is hatless.
Fluttershy's wings disappear as she runs to catch Philemena before she bursts into flame.
The Cutie Mark Chronicles
In Pinkie Pie's flashback, her Cutie Mark can be seen on her flank in the scene before she actually gets it.
Shots of the moon in the episode do not have Nightmare Moon's silhouette, even though the flashbacks take place at a point in time when she should still be imprisoned.
Party of One
When Pinkie Pie is interrogating Spike, right at the beginning, the shadow of Spike on the wall is not moving but static in a crouching position.
In the conga line in the end, each pony's tail should logically be between the hooves of the one coming behind her, but instead the hooves both cover the tail.
Watch the party hats in that whole scene. At first they all have patterns that correspond to their Cutie Marks. Over time though, some become generic, some have another pony's hat, and some disappear entirely.
During the "Pinkamena Party" sequence, the party hat colors are inconsistent. "Rocky"'s hat changes color at least twice.
The Best Night Ever
When Rarity's charming a couple of her neighbors, pay close attention to Noteworthy◊.
When Applejack sets up her stand and makes a sale, her shoes are mysteriously absent in a few frames.
Later in that episode, Rarity's golden tiara disappears for a frame during one of her temper tantrums.
Similarly to the example above with Pinkie's trombone, the harp player during the "Pony Pokey" segment is supporting his harp from the wrong side.
The Return of Harmony Part 1
In the opening shot, Cheerilee's face disappears for a few frames after the camera finishes zooming out.
The episode's title is displayed with two spaces between the words "Harmony" and "Part" instead of one.
The Stained Glass Window depicting the ponies and the Elements of Harmony changes many times before and during the time Discord is showing off his knowledge of the mane cast. In the scenes before he shows up, the window is normal. When he appears, Twilight disappears from the top, then in the next scene he's in the previously not present area Twilight is in, disappears again when Rainbow Dash charges the window, and finally reappears when he says that Twilight's got the most elusive element of all and when he dances on her head. One might chalk this up to his powers, though. In the same scene, Discord is depicted as a stone statue in one window, which has disappeared in its next appearance (shortly before Discord appears in the window personally) even though Discord came to life from a different window.
The long carpet in the tower corridor does not remain at all consistent (the trim, the pattern on the trim, and the center weave each disappear at random in every shot shot).
When the ponies discover the Elements of Harmony are missing, Pinkie Pie declares she's going to be outside in the chocolate milk rain and runs out of frame—but after the commercial break is in exactly the same position she had been before running out of frame, in the middle of the ponies, as if nothing had happened. (There is no indication that any time actually passed at all between those shots.) Then again, trying to make any sense of Pinkie Pie is doomed to failure.
At one point Discord seems to be missing his wings. Given their small size and the fact he's a Reality Warper, it could be explained he just made them disappear for whatever reason.
When the mane six split up in the labyrinth, Rarity (who's supposed to be hornless at this point) has her horn when Fluttershy screams.
The vision shown to Applejack involves everypony still hornless and wingless, except Twilight – but the close-up of her face shows her hornless too. Granted, it's a fake vision, but it's still probably not meant to be inconsistent like that.
Around the first time Applejack lies, her visible eye is the shape of Twilight's or Rarity's instead of the normal oval for one shot. While eyes in this show can be pretty expressive, there's no apparent reason for this, and it's unprecedented for her.
The Return of Harmony Part 2
Right after defeating Discord Rainbow Dash briefly has Fluttershy's cutie mark.
As the ponies enter Twilight's library, when Fluttershy stomps on the plants outside the door, they disappear for one frame.
Rarity's eyelashes disappear for a split-second slightly after Applejack's Han Solo wink in the finale.
Twilight opens a box containing thirteen cupcakes, all with pink icing. Worried that one has more icing than the others, she begins "fixing" them up, resulting in barely a dollop of icing on each cupcake. When she's putting the lid back on the box, not only do the cupcakes have the same amount of icing as they did when she opened the box, but they're all different colours.
Near the end, when Spike is watching Twilight and Celestia in the library, Twilight's mane and tail are as straight and groomed as they normally are. In the next shot of Twilight, her hair is back to being messy and unkempt.
When Twilight first shows up at the picnic, Rainbow Dash's wings are up. In the next shot, they're folded down. In the shot after that, they're up again.
When Pinkie Pie tells Twilight she's "such a crack-up," Pinkie is in front of Twilight, off of the blanket. In the next shot, she's with the rest of the Mane Cast, behind Twilight, and on the blanket (Though this is Pinkie Pie we're talking about).
After the background ponies stampede through the picnic, Rainbow Dash and the folded up blanket both disappear. Also, Pinkie Pie moves back quite a ways.
At the beginning of the Mayor's speech (specifically, when she says "Thank you, everypony"), the audience consists of the same group of ponies twice. That normally wouldn't be an issue, except this crowd includes the Cakes, who are not supposed to be duplicated.
When Luna says "Huzzah! How many points do I receive?," she has part of her hair from her season 1 design.
This happens several times throughout the episode, apparently due to her mane's design being changed very late in production.
One of the more common bloopers is inverted: when Applejack is covered in purple goop from Applebloom, her freckles are not missing when they're supposed to be.
During the race, Cloud-Kicker's baseball cap randomly glitches out for a couple frames, leaving only the brim.
The Cutie Pox
In "The Cutie Pox", Applejack's hat briefly disappears while Pinkie Pie is confessing to how many corn cakes she ate.
May the Best Pet Win!
When Rainbow Dash skids to a halt before saying "Guts!", a duck which is supposed to be in the background is layered improperly, so it appears to be floating in front of her face.
Right after Rainbow Dash says that she might want a pet, Fluttershy's mouth disappears for a couple of frames.
Fluttershy's wings briefly flap completely out of sync during the song.
Toward the end of the episode, there is a "through the binoculars" shot of Rainbow Dash being carried to the finish line on Tank the Tortoise's back. None of the ponies at the line are even wearing binoculars in the following shot.
Sweet and Elite
The number of Wonderbolts in the derby changes between shots.
Not only that, but the referee standing on the side of the track is an Earth Pony.
Though this might not actually be a blooper, but an instance of continuity. Remember the Cloud-Walking spell from Sonic Rainboom?
Secret of My Excess
As June Bug walks away from Spike, a glitchy third basket repeatedly appears and disappears.
Family Appreciation Day
Cheerilee has Parasol's tail (again) and trio-of-umbrellas cutie mark for two separate shots just before she talks to puppet Granny Smith.
Just as Mr. and Mrs. Cake are leaving Sugarcube Corner to deal with their catering gig, Pumpkin and Pound Cake are shown playing on the ground in the buff, despite their diapers having been changed not long before. The next shot with the twins in it has their diapers reappear.
Hearth's Warming Eve
The characters in the play raise a banner for Equestria, then the play ends, the actors take a bow, and the ponies sing. However, after the song begins the banner disappears for no apparent reason (it simply vanishes between shots of the stage, and doesn't reappear).
Fluttershy's walking animation skips slightly when she and the other ponies arrive in Canterlot.
The Last Roundup
There is a chase sequence between a stagecoach and a ponycart. Applejack, in the coach, looks over the back and down at Fluttershy and Rainbow Dash, who are harnessed to the cart and staring back at her. During the bit shown from the former's point of view, the two pegasi don't have wings (which should be visible, even if under the harnesses).
When Pinkie Pie is just beginning to freak out over Applejack breaking her promise, Fluttershy's tail is missing.
In the scene where Pinkie Pie is talking Applejack to the brink of insanity, Applejack is missing her cutie mark when she yells, "Noooooo! Make it stop!"
After Pinkie startles Fluttershy (leading Fluttershy to respond as such), her wings are notable missing right before she gets up; From the angle she's at, they should have still been visible.
The Super Speedy Cider Squeezy 6000
Just after Applejack tells Princess Celestia she "didn't learn anything," her eye is a lot larger than normal.
During the montage at the beginning where everypony is drinking cider, Cheerilee's eyes are the wrong color (they are supposed to be green, but appear here as magenta – the same color as background pony Berry Punch's).
Read It and Weep
After Daring Do escapes the death traps only to set off a few more, her mouth moves to form words, but all we hear is an annoyed groan. It looks very much like she's saying "Not again."
Inversely, while Applejack, Rarity, and Pinkie Pie are visiting Rainbow Dash, Applejack says "Go ahead and eat up," but the mouth-flap animation is far too short to match the line.
Spike's spines are missing from the back of his head in one scene in Twilight's library.
During a scene where Rainbow Dash is laying in the hospital bed, she turns her head and her mane completely disappears for one frame.
Hearts and Hooves Day
During the close-up shot of Mr. Waddle, his frizzed-up hair is back to normal for the one frame in which he faces the camera.
In the book that contains the recipe for the love potion: the first time it's shown to the audience (by Twilight Sparkle) the princess in the illustration appears to be an earth pony, but the other two times it's shown to the audience (by Sweetie Belle) the princess in the same illustration is now an alicorn.
The hour that the Crusaders have to cure Cheerilee and Big McIntosh of the love poison keeps switching between 4:00 to 5:00 and 5:00 to 6:00.
At the end, when Diamond Tiara is is knocked against the press, her hindquarters can also be seen standing with the Cutie Mark Crusaders in the next shot when they laugh at her.
A Canterlot Wedding - Part 1
At the end, there's an easy-to-miss one when Cadance, actually Chrysalis, uses her magic to capture Twilight. For several scenes, Twilight is on a small set of stairs. However, in the final scene, while Cadance/Chrysalis is walking away, looking behind her you can see that Twilight and the green flames engulfing her have moved onto a flat portion of the floor, and that there are in fact no visible stairs whatsoever in the hall.
A Canterlot Wedding - Part 2
During the sequence when the Mane 6 are running to the vault where the Elements of Harmony are kept, Applejack's hat disappears and reappears at least twice.
The Crystal Empire - Part 1
At the beginning of the episode, when the guard opens the doors, his eyes are teal. When he takes his helmet off, his eyes are brown.
Too Many Pinkie Pies
After a few of the Pinkies get zapped by Twilight for looking at the orange-frog, the number of Pinkies in the hallway drops dramatically.
Later in the same sequence, a change of camera angle causes the number of Pinkies to increase from eight to eleven for one shot.
One Bad Apple
While chasing the golden apple float, Scootaloo's wings disappear.
Just as Trixie banishes Twilight, Pinkie briefly regains her nose when she shouldn't have it.
As Twilight leaves Ponyville, her shadow is disjointed from her body. It returns to the proper place when she starts running.
When Twilight is performing at the end of the episodes, Shoeshine in the crowd in the upper left of the bleachers has no face.
Sleepless in Ponyville
During the second night's campfire, Rainbow Dash and Scootaloo both have their wings missing in several scenes.
Inside the cave, we first see Applejack in a dark green sleeping bag, and Apple Bloom in a light green one. In a different shot, the colors swap.
When Rainbow Dash flies away from the Mane Six in the beginning of the episode, the picnic blanket and mailbox both disappear.
Several times throughout the episode, Cloudchaser has the wrong cutie mark.
After Rainbow Dash finishes packing the clouds to stop her friends from falling, her uniform disappears.
Mentioned above, one of the Wonderbolt trainees is a hastily-recolored Wild Fire. Two brief shots forgot to recolor this pony and one shot of the chalkboard shows Wild Fire's cutie mark instead of the replacement one (a sunflower).
Just for Sidekicks
In the scene just before the Mane Six leave the library, the magical aura that is supposed to be around Tank's helicopter device is missing.
When Apple Bloom puts on her goggles, the strap that attaches them to her head never appears. In the same scene, some leftover red storyboard marks can be seen on Angel when he hugs Scootaloo.
After Spike hurries the animals back on the train in the Crystal Empire, Owlowiscious has a bow tie in a few scenes, which had never shown up before that point in the episode. In the same scene, Gummy briefly sports a collar.
When the Mane Six are walking off the train, both Rainbow Dash and Fluttershy are missing their wings.
At the end of the episode when Twilight and Spike walk into the library, part of Spike's leg is layered over his body.
Apple Family Reunion
When Applejack picks up Spike like a lighter, she briefly appears to be holding him with three hooves.
The painting of the "American Gothic" ponies briefly loses the pitchfork after Applejack looks at the night sky.
During the "Raise This Barn" song sequence, while Apple Bloom and Babs Seed are shearing a plank of wood, Babs's eyes are the wrong color (her eyes are supposed to be green, but in this shot they're orange like Apple Bloom's).
Towards the end of the episode, while Applejack is taking a bath, part of Granny Smith's eye is improperly layered.
The group photo at the end shows two young Apple family members as unicorns instead of earth ponies. When the shot zooms out into a photo frame, the two unicorns change to earth ponies.
Spike at Your Service
In the opening, when Spike is about to smell his feet, a group of bees in the upper-right hand corner of the screen is frozen in place.
When Spike is backed up against the cliff by the three Timberwolves, they all have a distinct crown shape in their shadows. None of the normal Timberwolves have a crown on their head; only the large Timberwolf at the end does.
When Spike takes the plate away from the table after serving pie to Applejack and Rarity, the pie is whole, when it should be missing a slice. In the next shot, the pie is properly missing the slice. In the same scene, Rarity's mane is briefly layered over her horn.
Keep Calm and Flutter On
Several times during the episode, the black part of Discord's mane disappears.
When Discord tempts Fluttershy with some ice skates at the frozen-over Sweet Apple Acres, the movement of his wings eventually de-syncs from the movement of the rest of his body.
Games Ponies Play
Just after the train crash, Fluttershy has Twilight's cutie mark.
During the cheer the Mane Six had practiced, Pinkie Pie has Twilight's cutie mark.
In several shots, the crystal ponies aren't properly "crystallized."
Magical Mystery Cure
In the scene where Rainbow Dash is trying (and failing) to tend to all the woodland creatures, she zooms off screen after locking Gummy in a bird cage; during her exit she has her own cutie mark instead of Fluttershy's.
In the scene where Fluttershy is trying to calm the woodland creatures in the cottage, when she says, "feel like giving Rainbow Dash a hard time," she briefly has her own cutie mark instead of Pinkie Pie's.
During the "What My Cutie Mark is Telling Me" song, part of the barn and background is layered over Pinkie as she's complaining about the water chute.
At the scene of the princess coronation, Cadance's hair is up in the ceremonial headdress from "Games Ponies Play." When she approaches Twilight later in the same ceremony, her hair is in its normal style.
During the scene on the balcony, Luna is wearing her normal crown, when she's supposed to be wearing a much more elaborate one.
During "What My Cutie Mark is Telling Me" Applejack sings "Can y'all give me a hand here?" despite they shouldn't know what hands are, confirmed by Rainbow Dash at the end of Equestria Girls.
Princess Twilight Sparkle - Part 2
When Discord is in Twilight's ear, there are briefly two Element of Magic crowns on her head.
When Fluttershy leaps onto the Mane-iac's cannon, it's in perfect condition. In the next shot, before she's actually started smashing the cannon, it's already wrecked.
During the song, when the rest of the Mane Six are circling around Fluttershy, the colors of Rainbow Dash's mane suddenly invert.
When staring up at Flutterbat in the tree, a flashlight is randomly floating between the Mane Six.
Soarin's goggles change style before and after the first commercial break: before the break they're the typical Wonderbolt-style with blue reflective lenses and a yellow strap, while after it they're clear lenses with a black strap. Also, while they're raised to his forehead before the break, they're back over his eyes after it.
After Rarity and Twilight pin up Cheese Sandwich's banner of Rainbow Dash, Derpy's wing is on backwards.
Rarity has wings when dancing on stage during the "Make a Wish" song.
When the rest of the Mane 6 chase off after Fluttershy, not only is Twilight missing her wings but Pinkie has Twilight's cutie mark.
The picture of the mane six that appears at the end of the opening◊ is frequently reused on official materials, sometimes with the ponies repositioned in order to add Spike and Princess Celestia, but often with one of Rarity's eyes glitched. And that isn't the only problem – the image was designed with the original positions in mind, so the non-visible parts of the ponies weren't drawn (as seen in one background◊ on The Hub's website). This is usually worked around by keeping the missing parts covered, with the other ponies or (less effectively) with the show's logo. But on at least one occasion, Twilight Sparkle's lack of front legs or a tail was left uncovered, creating Twiworm.
On the My Little Pony Facebook page, some images of the cast in their Nightmare Night costumes was posted as a teaser for the upcoming episode. This is all well and good, except that the caption identified Rainbow Dash's costume as a Wonderboltnote the MLP equivalent of the Blue Angels, when she's rather clearly dressed as a Shadowboltnote the Psycho Rangers counterpart to the Wonderbolts that Nightmare Moon cooked up in the pilot.
The initial release of Tank's trading card IDs him as belonging to Pinkie Pie (instead of Rainbow Dash).