Quote Originally Posted by karlyb View Post
Years ago I had a fluffy gray kitty and the vet told me it was a female. When I took her in for spay, the vet opened her up to take out the female parts - didn't find any. Then he looked under the tail and saw the male genitals. His explanation? "He's got a lot of fur." Poor cat had both abdominal incision and a sore butt.
Our "little" Runt had both an abdominal incision and a sore butt, but he had a cryptorchid (one testicle didn't drop)

The way we tell boy from girl: spot = boy, slot = girl
For some reason, we (personally) are able to tell better if we hold them on their back, in our hand, and look at their butt "upsidedown"
Obviously this method works easier with kittens