Twilight Sparkle

Twilight Sparkle is a purple unicorn and a very talented unicorn when it comes to performing magic. She is Princess Celestia's most faithful student who was sent to Ponyville to make preparations for the Summer Star Festival, but also to make some friends. She was incredibly reluctant too, due to focusing on her task, but also because she worried about the possibility of Nightmare Moon, an evil version of Celestia's younger sister Princess Luna, coming back after 1000 years and creating an everlasting night. The possibility became reality, but with the assistance of Applejack, Pinkie Pie, Rainbow Dash, Fluttershy and Rarity, five friends that Twilight met while in Ponyville, they harnessed the power of the Elements of Harmony and defeated Nightmare Moon, returning her to Princess Luna. Since then, Twilight has stayed in Ponyville with her friends and reporting to Celestia about every new lesson she's learned about friendship. Twilight also is Thomas's love interest.

Trivia

 * Twilight will meet the FT Squad in The FT Squad's Adventures in My Little Pony: Friendship is Magic. Her element of magic will be shared with the main six members of the FT Squad; Kyle the Otter, Rudy the Alligator, Dennis the Frog, Cassidy the Pelican, Kimmy the Elephant and Kaytlin the Otter.
 * Twilight will guest star in The FT Squad Meets the Hunchback of Notre Dame and The FT Squad's Adventures with the Winx Club.
 * Twilight will make occasional guest appearances in The FT Squad's Adventures With Phineas and Ferb, and will officially guest star in The FT Squad's Adventures With Phineas and Ferb: Summer Belongs to You.
 * Twilight and her friends joined Thomas the Tank Engine and his friends at the end of Thomas' Adventures of My Little Pony Friendship is Magic - A Canterlot Wedding (Full Movie).
 * Twilight is very intelligent and provides useful knowledge for the FT Squad when needed.