Trixie Lulamoon

Trixie is a unicorn pony and a traveling magician who is featured as the main antagonist of Boast Busters and Magic Duel and makes background appearances in Bridle Gossip and The Return of Harmony Part 1. She tends to speak in the third person and refers to herself as "The Great and Powerful Trixie." Trixie visits Ponyville with her one-mare show, in which she shows off, extremely exaggerates, and boasts about her abilities. The name Trixie is a diminutive form of Beatrix.

But she then reforms at the end of the episode Magic Duel.

Personality
Trixie first appears in Boast Busters, where she assumes a very theatrical personality and speaks dramatically in the third person, posing and setting off fireworks to complete the full effect.

Twilight Sparkle's positive, helpful, and humble attitude is contrasted by Trixie's over-the-top boasting and arrogant nature. Trixie claims to have saved Hoofington from an attack by an ursa major. However, when confronted by an ursa minor, she admits that her tale was fabricated and that even the ursa minor was an opponent far too powerful for her to contain. This is the only point in the episode where she drops her "Great and Powerful Trixie" persona and speaks in the first person. Despite this brief display of honesty and fear, her frequent showboating alienates the other ponies and classifies her as an antagonist of the series. In Magic Duel, Trixie returns with her magic augmented by the Alicorn Amulet and she uses this power to take revenge on Twilight by cheating in a magic duel, banishing her from Ponyville and subsequently setting herself up as the leader of the town. She shows no qualms about using innocent ponies (Rarity, Rainbow Dash, Spike, Snips and Snails) to prove her power, nor does she seem to care when a spell nearly takes out another (Shoeshine). Through the episode, she has Mayor Mare trapped in a cage, forces other ponies to do manual labor for her, and claims to not "trust wheels." She was also easily manipulated by Twilight Sparkle into a rematch duel so she could prove that she was still better, which eventually lead to her downfall. However, upon removal of the amulet and the loss of her power, she accepts her defeat against Twilight, unlike her first visit to Ponyville, and meekly seeks forgiveness for how she treated her and her friends. At the end of the episode, she once again drops her persona and speaks in the first person, but only for a few seconds before she refers to herself as the "Great and Apologetic Trixie."

Trivia

 * Trixie will become Winnie the Pooh's enemy, but later turns good, in Pooh's Adventures of My Little Pony Friendship is Magic.
 * Trixie will become Thomas' enemy, but later turns good in Thomas' Adventures of My Little Pony Friendship is Magic - Magic Duel and will make her guest starring appearance in Thomas and Twilight Sparkle in Fantasmic (Disneyland Version), Thomas and Twilight Sparkle's Adventures of Pirates of the Caribbean: The Curse of Black Pearl, Twilight Sparkle's Adventures of Space Jam, Thomas and Twilight Sparkle's Adventures of Pirates of the Caribbean: Dead Men's Chest, Thomas and Twilight Sparkle's Adventures of Pirates of the Caribbean: At World's End, Thomas and Twilight Sparkle Gets Frozen, Thomas and Twilight Sparkle Visits The Haunted Mansion, Thomas and Twilight Sparkle Spends the Night at the Museum, Thomas, Twilight Sparkle and the Adventures of Rocky and Bullwinkle, Thomas, Twilight Sparkle and the Adventures of Rocky and Bullwinkle, Twilight Sparkle's Adventures of Sleeping Beauty, Thomas and Twilight Sparkle's World of Color, Thomas and Twilight Sparkle in Fantasmic (Walt Disney World Version), Thomas and Twilight Sparkle Spends the Night at the Museum 2: Battle of the Smithsonian, Thomas and Twilight Sparkle's Adventures of The Prince and the Pauper, Thomas and Twilight Sparkle's Adventures of Looney Tunes: Back in Action, Thomas and Twilight Sparkle's Adventures of Cloudy with a Chance of Meatballs, Thomas and Twilight Sparkle's Adventures of Cloudy with a Chance of Meatballs 2, Thomas and Twilight Sparkle's Adventures of Disneyland Fun and Thomas and Twilight Sparkle's Adventures Chronicles helping any friend in need.
 * Trixie will become Brian Griffin's enemy in Brian Griffin's Adventures of My Little Pony: Friendship is Magic - Magic Duel but will reform, and will guest star in Thomas and Twilight Sparkle's Adventures of Family Guy: Road to the Multiverse, Thomas and Twilight Sparkle's Adventures of Mighty Morphin Power Rangers: The Movie, Thomas and Twilight Sparkle's Adventures of Turbo: A Power Rangers Movie, Thomas and Twilight Sparkle's Adventures of Family Guy: Turkey Guys, Thomas and Twilight Sparkle's Adventures of Futurama: The Beast with a Billion Backs, Thomas and Twilight Sparkle's Adventures of That 70's Show, Brian Griffin enters The Polar Express, Brian Griffin's Adventures of National Lampoon's Vacation, Brian Griffin's Adventures of National Lampoon's Christmas Vacation, Brian Griffin visits Jurassic World, Brian Griffin's Adventures of Power Rangers: S.P.D. and Brian Griffin's Adventures Chronicles.
 * Trixie will be Jimmy Neutron's enemy, but turns good in Jimmy Neutron's Adventures of Pokemon: Jirachi Wish Maker and then later she joins his team in Jimmy Neutron's Adventures of The Lord of the Rings: The Return of the King.
 * Trixie is also Prince Blueblood's Wife.
 * Trixie will become an Alicorn in Yuna's Destiny Part 2.
 * Trixie along with Twilight Sparkle and Sunset Shimmer are Princess Yuna's Mentors.