Princess Tutu

Ahiru (or “Duck” in English) is a clumsy, good-hearted and sweet girl who has a big secret. She’s actually not a human at all. The mysterious Drosselmeyer morphed a young duck into a girl to give her a mission: help a Prince get the parts of his heart back. She then becomes a 14-year-old ballet student in Gold Crown Town, Germany. With the help of a magical pendant from Drosselmeyer himself, she morphs into Princess Tutu. She performs magical dances to ease the pain of people in her town and purify their bad feelings. The duck girl works eagerly to restore each part of the Prince’s heart back little by little.

Synopsis from Anime News Network