In S5E5 of Lost Girl, a character named Bo gradually transforms into a black cat.
http://www.dailymotion.com/video/x4t...r-lucky-fae_tv
Her transformation begins at the 25:00 mark. Her hands turn into paws, she grows a tail, and near the end of the episode she has whiskers and a snout when she's laying in the cardboard box. She also does cat like things (purrs, grooms herself, etc.)
At the 37:25 mark there's a nice close up of her tail swinging above her bum