Ananova reports a case of a cat in China that has grown wings
. The owner of the cat, Granny Feng, says, ""At first, they were just two bumps, but they started to grow quickly, and after a month there were two wings."
Ananova isn't the most reliable of sources, but I don't see any reason to doubt this story. Winged cats are a rare, but entirely possible phenomena. I could have sworn they'd been covered on the MoH before, but apparently not (at least I can't find any mention of them after doing a search).
offers the best discussion of winged cats, explaining that the "wings" are typically mats of fur, or the result of either a congenital deformity or a skin condition. (Thanks, Kathy)