My cat, some time after going #2 in the litter box, kinda walks on his butt as if wiping or scratching it. (It's hilarious to watch). Well before he did it on a dark carpet so I didn't see stains, but then I noticed some "wiped poo" on the white window sill, and a little on my bed sheets where he sleeps (now I put his sleeping blanket there, so that he'd do it there) . It looks like he is using these surfaces as toilet paper. Is this normal? Part of cat cleaning himself? His poo in the litter box is perfectly normal.