Cheerilee and the kids are visiting the world famous Canterlot Sculpture Garden, where there are statues representing friendship, victory, and... a tall slender fellow with a head of a pony and a body made of many different animals, like a lion's paw and a snake's tail. Cheerilee asks the class what that represents, and Cutie Mark Crusaders respond with a variety of answers, calling Scootaloo a dodo in the process.The Cutie Mark Crusaders begin to fight amongst each other until Cheerilee explains that, in a way, they're all right. The statue represents discord, and because they demonstrated it so well they have to write an essay. Cheerilee and the kids head off and did that statue just laugh?Back in Ponyville, Rainbow Dash is flying around when she is hit by a low-flying pink cloud. Now, we know this is a Sugar Bowl, but it's been established that clouds do not move on their own outside the Everfree Forest. They are also not made of cotton candy. Suddenly, cotton candy clouds are everywhere and they pour out rain made of chocolate milk.Soon the rest of the Mane Six meet up at Sweet Apple Acres, where cornfields are turning into popcorn, apples are growing to mammoth sizes, and rabbits are growing deer legs. The girls manage to calm the candy storm and the mutated animals through teamwork, only for Spike to burp up an emergency letter from Princess Celestia.At the palace, Celestia informs the girls that an old foe has returned...Discord, the mischievous Spirit of Disharmony... and gives some backstory on Equestria. Discord once ruled the land in eternal chaos and unhappiness, until Celestia and Luna discovered the Elements of Harmony and turned him into a garden ornament. However, since Celestia and Luna are no longer connected to the Elements (probably because of that whole Nightmare Moon business), the spell on Discord has lifted. It is now up to our heroines, the champions who defeated Nightmare Moon and redeemed Princess Luna, to wield the Elements of Harmony once again to defeat this dark god of chaos....But they're missing! Who could have stolen the Elements of Harmony? The stained-glass windows begin to move by themselves, all handiwork of the culprit, Discord.It seems Discord has "borrowed" the Elements, and he already knows all about our heroines and which Element of Harmony they represent. Celestia is getting impatient with Discord's escapades, and let us remind you that she usually has the patience of a saint. Discord gives our girls a riddle.
Discord: To retrieve your missing Elements, just make sense of this change of events. Twists and turns are my master plan, then find the Elements back where you began.
Twilight believes Discord is referring to the hedge maze out back... where the children were arguing earlier. Surely with the magic of flight Rainbow Dash will find the Elements in no time. That is, if her wings were still on her. Fluttershy's wings and the unicorns' horns disappear as well, and Discord appears! He says that it's time to play a game. The first rule is no flying or magic. The second rule is everypony has to play, or the game is over.The girls enter the maze and, with their first united step, are instantly divided by Discord's magic. He then takes the time to manipulate all of Twilight's friends to reject the elements that they represent, finishing the job with magic and causing their colors to become desaturated.
Discord uses piles of talking apples claiming to be the "Keepers of the Grove of Truths" to show Applejack the "honest truth" of what will happen; the Circle of Friendship will be broken. After facing her with how much the truth can hurt and the idea that lies might be easier, he makes her chronically dishonest (that is, lying through her teeth).
He uses balloons with the faces of Pinkie's friends to laugh at her, suggesting that her friends don't really like her. After a brief "torture" session consisting of all the balloons laughing at her, Discord hypnotizes Pinkie, making her unhappy and unfriendly.
He tempts Rarity with a beautiful shiny something, and she becomes enchanted as soon as she succumbs to the temptation to dig it out. It turns out to be a diamond bigger than herself that she becomes extremely possessive of. However, the "diamond" is actually a giant rock; Rarity is brainwashed into seeing it as a jewel.
He tries to turn Fluttershy against her friends, but she has too much trust to think they abandoned her, and too little ego to mind being thought of as weak or being criticized... so he just goes ahead and magics her into being cruel anyway.
He presents Rainbow Dash with conflicting loyalties: stay in the maze and continue searching for her friends and the Elements, or take back her wings and go save Cloudsdale from destruction, betraying something she cares about regardless of what choice she makes. Of course, he hypnotizes her before she can make the choice.
Twilight meets up with all her friends, who are all now the opposite of their Elements, and they spot the disloyal Rainbow Dash flying away. The game is over and Discord has won! Black clouds and lightning abound! All is lost, a storm of chaos has arrived! Equestria is doomed!
Tropes present in this episode (YMMV tropes can be found here):
Actually Pretty Funny: When Discord stands on the head of an image of Twilight Sparkle and does a little dance, Pinkie Pie can't help but laugh. She does represent the Element of Laughter, after all.
And I Must Scream: As the brainwashing effect by Discord takes place on them, the mane ponies could only be aware that they had fallen into Discord's traps.
Apple of Discord: Played quite literally with Applejack by Discord himself, and more figuratively with everypony else.
Art Shift: A minor one. Everypony else remains the same, but Discord's first appearance takes place as he magically slinks around the stained glass windows of Canterlot Tower.
As You Know: Celestia and Discord take a few moments to remind the viewers of the series premiere and what Element each pony represents.
Ascended Meme: In "Stare Master", Apple Bloom calls Scootaloo a chicken. Naturally, the fandom took this and made it into a meme. In this episode, she gets called a dodo, another flightless bird.
Scootaloo: Don't call me things I don't know the meaning of!
Awful Truth: Discord's manipulation of Applejack starts by telling her that the truth can hurt, and there are some truths she'd rather not know.
Bad Bad Acting: Fluttershy using "reverse psychology" on the animals to get them to eat away the candy clouds and popcorn.
Bad Liar: Applejack was always a bad liar, but this episode takes it to a new extreme. Corrupted Applejack, in addition to her lies being obvious, bites her lip and makes shifty eyes every time she lies. Her "poker face" became a meme within a few hours of the episode being aired.
The Bad Guy Wins: The episode ends with Discord successfully brainwashing all of Twilight's friends and letting his reign of chaos loose on Ponyville.
Became Their Own Antithesis: Discord's hypnosis of the mane cast essentially turns them into their own evil counterparts, complete with color fading. Applejack becomes a chronic and impulsive Bad Liar, Pinkie Pie becomes deadly serious and perpetually angry, Rarity becomes self-absorbed, Fluttershy becomes a total Jerkass, and Rainbow Dash abandons her friends.
Discord's goal behind his little "game" was to do this to everyone (except Twilight) and he succeeds, although he has to cheat with Fluttershy.
Twilight gets this by proxy, as Discord reunites Twilight with her friends one by one after breaking them. She can't figure out what's wrong with them, and she has to suffer through her friends treating her like dirt. The look on her face after getting verbally assaulted by the corrupted Fluttershy paints a clear picture that she's been broken, too...
Conflicting Loyalty: How Discord breaks Rainbow Dash. She is forced to choose between her loyalty to her friends and her loyalty to Cloudsdale. She chooses Cloudsdale after Discord puts the whammy on her, which ends Discord's twisted game in his favor.
If one pays attention to Discord's component parts, he's got pieces from every species who played an antagonistic role in season one. One of his horns is like a unicorn and he has a horse (or possibly buffalo) leg (Trixie and possibly the buffalo), a lion paw (the Manticore from the pilot), a griffin-like mane body and arm (Gilda), a green dragon leg (the dragon Spike encountered), a red reptilian tail (the red dragon from "Dragonshy"), a pegasus wing (Nightmare Moon), and a bat-like wing (which looks a lot like the cockatrice).
Apple Bloom and Sweetie Belle make a subtle one to their respective sisters' behavior in "Look Before You Sleep".
Apple Bloom: [to Scootaloo] Cool... if you were actually victoryful at somethin'. Sweetie Belle: That's not a word!
The Dark Times: Celestia refers to an era in which Discord ruled and caused endless suffering for Equestria. It is depicted in a stained-glass window as Discord holding ponies by puppet strings over a pit of fire.
Despair Event Horizon: All of the protagonists end up broken by Discord, and then resort to awful things in their opposite personalities.
Deus ex Machina: Lampshaded and averted when Twilight arrives with a "spell that will fix everything". It doesn't work, possibly because of the influence of the God of Chaos himself.
Divide and Conquer: Discord manages to physically split the group up so he can pick them off one by one. In the end, Twilight Sparkle was the only one he didn't get to. That doesn't matter, though, because she's nothing without the others.
Doomed Hometown: Discord uses an image of this to convince Rainbow Dash to abandon her friends.
Downer Ending: Discord wins this round, and has successfully brainwashed all but one of the mane cast. The final shot of the episode is Twilight Sparkle watching in shock and despair as he lets loose a storm of chaos on Equestria.
Dramatic Irony: We know what Discord is trying to do after he gets to Applejack, but the rest of the characters don't, leaving us to watch helplessly as they fall victim to Discord one by one.
Dramatic Thunder: Discord doing his Evil Laugh. Since he's a Reality Warper with a flair for the dramatic, this is probably intentional on his part. Happens again at the end as he stands posed to plunge Equestria into never-ending chaos.
Eldritch Location: The hedge maze gets really weird, to the point that it's once shown as an Escherian structure with ground level of varying orientations. The rest of Equestria is liable to go this way too, if Discord gets his way.
Embodiment of Vice: Each member of the "mane 6" is corrupted by Discord to represent the antithesis of their Element of Harmony:
Pinkie Pie represents despair
Fluttershy represents spite/cruelty
Applejack represents deceitfulness
Rainbow Dash represents betrayal and aloofness
Rarity represents greed and envy
In part 2, Twilight Sparkle briefly represents severance and disharmony
Establishing Character Moment: The Mane cast each gets one in the first scene to refresh everyone of their personalities. Discord also gets one saying there's no fun in making sense.
Et Tu, Friends?: From the corrupted True Companions' twisted point of view, they believed that they were betrayed by their friends when in reality, they were brainwashed by Discord into doing so. In general, Twilight herself gets this whenever she finds her friends, one by one, acting different from themselves.
Evil Plan: Discord wants to return Esqueria to the days his rule; eternal chaos.
The Eyes Have It: Discord first introduces himself to the ponies by manifesting himself as part of the stained-glass windows in Celestia's castle.
Failsafe Failure: Borders on Lampshade Hanging. Twilight learns a "failsafe spell", which she believes will counter the wacky weather plaguing Ponyville. It fails. She says, "My failsafe spell... failed!"
Rainbow Dash: I'll always be loyal to the princess! Discord: We'll see about that...
When it rains chocolate milk on Ponyville, Rainbow Dash tells Applejack that it is simultaneously raining cola on Cloudsdale, but not to worry because she will help her friends before going off to help her town. This mirrors the choice she is given later on.
When Discord first appears in Canterlot Tower, and drifts into the next window, he is leaning on one of the images. He says "It's been quite lonely imprisoned in stone, but you wouldn't know that, would you, because I don't turn ponies into stone!" and then he knocks on the image he's leaning on. Specifically, her head. The image is a picture of Fluttershy.
Fluttershy is the only one of the mane six who Discord can't corrupt with his words alone. Instead, he has to use magic to brute-force brainwash her.
From Bad to Worse: How much worse can Twilight's mission get? First Discord returns, then he steals the Elements of Harmony then he divides the Mane Cast then he corrupts five of them....
The GM Is A Cheating Bastard: Discord stacks the deck heavily against the mane six by taking away their magic and wings, separates them the instant they step into the forest maze, and proceeds to turn all of them against each other through hypnosis. He likes to soften them up before using it, but when it doesn't work with Fluttershy, he just zaps her with magic. To top it off, he gives Rainbow Dash her wings back, then uses her as an excuse to end the game prematurely.
Gold Fever: Rarity's love of gems is used by Discord to break her.
Hope Spot: Downplayed twice in the maze. Rarity snaps out of it when Discord's trying to mess up her mind, but after a few seconds of fighting it, she falls for his trap; Fluttershy can resist him, but this being Discord, he just magically brainwashes her anyway. Played straight in the library, when Twilight finds the Elements, and it looks as if she can lead her friends to victory, only to realize no, they were too far gone and Discord still wins. Luckily, she later finds another way.
Idiot Ball: Twilight, throughout much of this episode on the next. Despite her friends not acting like themselves at all, she doesn't appear to suspect that her friends are under Discord's spell in any way; she acts like they've just suddenly decided to become Jerkasses for no apparent reason.
She does, at least originally, cite "stress" as the reason she thinks they're acting up, and tries to tell herself that AJ's lies are just part of her imagination.
Incorruptible Pure Pureness: Discord is unsuccessful in his attempts to break Fluttershy, forcing him to simply hypnotize her the old fashioned way.
Insult Backfire: Discord tries to make it seem like Fluttershy's friends are insulting her, but she interprets it as them trying to help her improve herself.
Jaw Drop: The mane cast and Celestia when it's revealed that the Elements of Harmony have been stolen.
Jerkass Ball: All of the corrupted ponies, especially Pinkie Pie and Fluttershy.
Just Toying with Them: Without the Elements, the ponies wouldn't stand a chance against Discord if he didn't choose to play the maze game with them... nor do they, as it turns out, even then, as he doesn't follow any rules himself.
Knighting: Princess Celestia does this to Twilight just before everypony goes off to retrieve the Elements from Discord. There's no ceremony involved, just the shoulder-to-shoulder motion with her horn as a stand-in for a sword.
Knight of Cerebus: After a season of mostly Slice of Life episodes, we get a villain who is dangerously competent despite his silliness. Even Nightmare Moon was a relatively manageable threat in comparison. By the end of the episode, he has subjected everyone but Twilight to Mind-Control Eyes and Break the Cutie in a truly frightening fashion.
Large Ham: Discord doesn't settle for a ominous dark clouds; he needs cotton candy clouds that rain chocolate milk. He deliberately invokes dramatic lightening to accompany his Evil Gloating.
Laughably Evil: Combined with his exceptional competence and malice, Discord also has the sharpest wit and zaniest moments of the Rogues Gallery.
Lecture As Exposition: Cheerilee in her role as teacher explaining just what "discord" means, which, while a vocabulary question, is highly relevant for the plot. The Cutie Mark Crusaders are put to do even more of the exposition for the audience by coming up with more common related words and acting discordantly, but Cheerilee is the one to point this out, too.
Mass Hypnosis: Everyone (except Twilight, Spike and probably Princess Celestia), courtesy of Discord.
Mass "Oh, Crap!": The looks on everypony's faces◊ (even Pinkie, though it doesn't last long) when the chest containing the Elements turns out to be empty. The look of abject horror on the normally placid-faced Celestia really underscores how bad this is.
Meekness Is Weakness: Discord tries to use this trope to hypnotize and corrupt Fluttershy, but it doesn't work.
Metaphorically True: When Applejack asks the pool that shows the truth what will come of their mission, she sees the Mane Six's friendship ending. What was true... as far as it goes.
The end of the episode. Discord has beaten the Mane 6, brainwashed most of them into betraying their elements and still has the Elements of Harmony in his possession. During his final gloat, he opens an inverted umbrella that meows before a lightning strike.
Mythology Gag: By taking away their wings, Discord effectively turned Rainbow Dash into her G3 incarnation and Fluttershy into Posey.note There was a G3 earth pony Fluttershy, but only as a toy and with a completely different color scheme.
Never Trust a Trailer: The preview footage released made it seem like Discord would be powerful, but more silly and lighthearted, which disappointed a few people expecting a more Darker and Edgier villain. As such, many were taken off-guard by how sadistic and cruel he really is.
Nice Job Breaking It, Hero: Twilight's immediate assumption that the solution to Discord's riddle is that he's hidden the Elements in the maze leads the Mane Six on an entirely fruitless search.
Offscreen Moment of Awesome: It's explained that 1,000 years ago, Celestia and Luna rose up against Discord's reign of chaos and terror and brought it to a halt by turning him to stone with the Elements Of Harmony. We don't know much about what happened, but it certainly sounds awesome; the stained glass resembles a Yin-Yang Bomb.
OOC Is Serious Business: Princess Celestia paces nervously and acts grave. Then she's surprised and shocked. Then she has no patience for fooling around with Discord. Until now, we'd never seen her any other way than calmly in control of the situation, with an appreciation for mischief and idiosyncrasy to boot. The simple fact she takes Discord so seriously and is so unnerved by his reappearance is the first sign he's a lot more dangerous than he appears to be.
Order Versus Chaos: In a world where Harmony is evidently the most powerful force for good, it's not surprising Discord would be embodied with similar strength.
Pragmatic Villainy: Discord might have no issues tormenting ponies with his mind games and insane challenges, but turning them to stone is right out. Then again, Why would he want to use Taken for Granite on anybody? There's no fun and chaos in that!
Rage Quit: Discord's reaction to Fluttershy beating his mind games. Up until then (and afterwards), he treats it like a game, but he reacts by getting furious, brainwashing her, then leaving in a huff.
Discord himself has a tendency to slip into rhyme when telling riddles.
Sadistic Choice: How Discord gets to Rainbow Dash. He makes her choose between abandoning her friends or letting Cloudsdale be destroyed. No matter which she chooses, she goes against her Element because she's betraying something she cares about.
Sanity Slippage: The corrupted mane ponies spends the two-part episode having their misbehavior made worse every passing minute.
Discord: Well... it must be so upsetting to know how weak and helpless [your friends] think you are. Fluttershy: Not at all. I am weak and helpless and I appreciate their understanding.
Self Fulfilling Prophecy: Invoked by Discord when he shows Applejack a vision of her friends breaking up and uses it to corrupt her. Everyone's corruption is, of course, posed to break their friendship as we move into the next episode. However, the vision wasn't a necessary component for it happening, and it was significantly false in detail.
Shaggy Dog Story: Not only does the ponies' quest in the labyrinth fail, the Elements were never in the labyrinth to begin with.
Title Drop: Ms Cheerilee calls the Cutie Mark Crusaders "My Little Ponies".
Celestria also calls the Mane Six "My Little Ponies" when she wishes them luck looking for the Elements in the maze.
Discord also calls Mane Six "My Little Ponies" when he "wins"
Virtue Is Weakness: Discord manages to emotionally break the mane six (right before hypnotizing all but Twilight) by explaining how the virtues represented by the elements of harmony are weaknesses. Specifically, honesty causes others to know things you don't want them to know, laughter hurts the feelings of the one being laughed at, kindness opens yourself up to being abused by others, generosity prevents you from getting the things that you want, loyalty means nothing when you can't be in two places at once and have to choose between two loyalties, and in general harmony is pointless as its own elements lead it to collapse on itself.
World-Healing Wave: Twilight tries one, but it fails horribly; see Failsafe Failure above.
Xanatos Gambit: Discord's Sadistic Choice to Rainbow Dash. The purpose of all his mind tricks was to get them to betray their Element Of Harmony, Rainbow Dash's being Loyalty. By forcing her to choose between two conflicting loyalties, Rainbow Dash is left with no choice but to betray something she truly cares about.