surprise

I took the cat to the vet over the weekend and found out that my cat is in fact a neutered MALE. I don't really know how to react to this. The person I adopted Kitty from and the first vet who saw Kitty all thought she's a female cat. Do cats change gender over their life time? Or maybe I took the wrong cat home that time in the cat hotel. Oh well, I guess now that she's a he I can get off Kitty's case about losing weight.