One of my boys has had this strange issue for a while where strange white stuff would appear on his butt. It would eventually go away on its own, so I didn't think much of it. Today I was grooming him and saw the strange white stuff was coming back. The brush did little to nothing, so I curiously tugged a little on the white stuff. Immediately, some of the white came off with a clump of fur sticking out of it, and I realized it was old skin or something? (I'll take a picture if it shows up again.) I'm not too worried, as its very minimal on his butt, he barely pays attention to it, and his brothers don't have it, I'm just curious what it is. The patches of white easily come off along with whatever fur is on it.