Discord

Discord is a spirit of chaos who first appeared as the antagonist of the season two premiere "The Return of Harmony". Primarily characterized as a nonsensical trickster, he is a Greek mythology-inspired creature called a "draconequus" (from the Greek words meaning "dragon horse"), a serpentine being with a pony's head and numerous different animal parts, symbolizing his inharmonious nature. It is shown in the series' distant past that he was opposed by Princesses Celestia and Luna for tormenting ponies with his reality-bending powers, and he similarly faces the Mane Six during the premiere; both times, the ponies use the Elements of Harmony to turn him to stone. In the season three episode "Keep Calm and Flutter On", Discord is released under Celestia's decree to reform himself, which he does after Fluttershy treats him like a friend. He appears in later episodes as a reluctant ally of the Mane Six, occasionally causing mischief while struggling to become a better friend to them. He is also a huge fan of Code Red.

Trivia

 * Discord will become Pooh's enemy until after reformed by Fluttershy in the future.
 * Discord is also friends with Gloomius Maximus, before he (Discord) truly reformed.
 * Discord will become the FT Squad's enemy in The FT Squad's Adventures in My Little Pony: Friendship is Magic, but will later become an ally after getting reformed by Fluttershy.
 * Discord will meet Team Robot In Team Robot &amp; The Mighty Morphin Power Rangers The Movie.
 * In My Little Pony: Friends Forever Issue #2, the Crusaders work with Discord, who makes a reality bubble for them and creates various scenarii in which they might earn their cutie marks. When Discord's reality bubble nearly covers all of Ponyville, the Crusaders put a stop to it. They thank Discord for his efforts and make him an honorary Cutie Mark Crusader.
 * Discord is also Catrina's Boyfriend.
 * Discord will become Thomas' enemy from Thomas' Adventures of My Little Pony Friendship is Magic - The Return of Harmony (Full Movie) until Discord will be reformed after Thomas' Adventures of My Little Pony Friendship is Magic - Keep Calm and Flutter On, but in Thomas' Adventures of My Little Pony Friendship is Magic - Twilight's Kingdom, he turn back to the dark side after Tirek aids him to steal stealing all the magic in Equestria in exchange for freedom to cause chaos on his own accord, only to be betrayed and drained of his magic by Tirek later. Having learned how truly important friendship is, Discord fully reforms, vowing to be a better friend to Thomas a nd will be making his guest starring appearance helping any friend in need.
 * Discord will appear in Pooh's Adventures of The Harry Hill Movie as a reformed character and will be joining Pooh and his friends at the end of the film.
 * Discord will meet Nighlock and his team in Pooh's Adventures of The Myth of Burton.