Princess Tutu

Princess Tutu (プリンセスチュチュ Purinsesu Chuchu) is a magical girl anime series created by Ikuko Itoh in 2002 for animation studio Hal Film Maker. It was adapted as a 2-volume manga illustrated by Mizuo Shinonome. Both the manga and anime series were licensed by ADV Films. Princess Tutu follows Duck (Ahiru in the original anime and manga, meaning "duck"), a duck who was transformed into a young girl and takes ballet at a private school. She becomes enamoured of her mysterious schoolmate Mytho, and transforms into Princess Tutu to restore his shattered heart. Mytho's girlfriend Rue transforms into Princess Kraehe to frustrate Tutu's efforts, and Mytho's protective friend Fakir discourages Mytho's burgeoning emotions. When it becomes apparent that Duck, Rue, Mytho, and Fakir are meant to play out the characters in a story by a long-dead writer named Drosselmeyer, they resist their assigned fates and fight to keep the story from becoming a tragedy.

Other Sources
Review of Princess Tutu at Anime Academy