Fruits Basket

Fruits Basket (or Furuba) is a romance manga/anime and revolves around the life of the teenage girl Tohru Honda. Tohru is and orphan who has been living in a tent all on her own until she met the Sohma family. Yuki Sohma and Shigure Sohma invite her to live with them and she finds out about the Sohma family secret. Whenever one of Sohma family that is posessed by a zodiac spirit is hugged by a member of the opposite sex, they transform into their zodiac spirit's animal. For example, when Tohru hugged Yuki he transformed into a rat because he was posessed by the spirit of the rat.