Arse dandruff

also known as poo-flakes and Butt crumbs.

small specks of poo that fall down on to the toilet seat while wiping. Particularly visible on white toilet seats (but carpets do an excellent job of concealing them). Usually observed among those with hairy cracks and high-fibre diets.

Son: Dad, did Uncle Jim come to visit again?
Father: Yes, why do you ask?
Son: I saw some arse dandruff on the toilet seat.