Discord

Discord is the enermy of Thomas and Twilight Sparkle. Discord will make his first appearence in Thomas and Twilight Sparkle Goes to FernGully: The Last Rainforest where he joined forces with Diesel 10, Queen Chrysalis and Hexxus to get his revenge on Twilight and her friends for turning him back into stone after he cause choas in Ponyville.

He also in the Bowser side in Super Mario and Friends new Adventure.

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 is also best friends with Diesel 10.
 * Discord became Roary and Theodore's enemy until reformed by Fluttershy, Iago, Bubbles,.
 * In the Twilight's Kingdom Part 1, Princess Celestia chooses Discord over Princess Twilight to help track down a villain. He appears before the Mane 6, Roary, Theodore and their whole team and gives Twilight her journal, marking several entries for her. Twilight, Roary, Theodore and Leonardo later discover the common theme of these entries having a connection to the mysterious chest at the Tree of Harmony. Later on, Discord is convinced by Tirek into returning to his old ways of chaos. He then assists Tirek in consuming the magic of all three pony races.
 * And in Twilight's Kingdom Part 2, Discord helps Tirek take over Canterlot before targeting Ponyville. He reveals his treachery to Twilight's friends, Roary, Theodore and their whole team, causing Fluttershy to break down sobbing. However, Discord is himself betrayed by Tirek and drained of his powers. It is ultimately Discord who helps Twilight discover her key by giving her a trinket that Tirek had previously given him, which Tirek had previously received from his brother Scorpan. He then truly reforms at last, having realized the true importance of friendship. At the end of the episode, he is accepted by the other ponies and is seen celebrating with them before offering a bouquet of flowers to Celestia and winking at her.
 * Discord may be reformed in the real seires but he remains a villain in most adventures
 * Discord is also Willy's arch enemy.
 * 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 along with Coco Pommel, Spitfire and The Wonderbolts, Cheese Sandwich, Seabreeze and Silver Shill are good friends with Gusto Gummi.