Skidmarks
Definition: One whose poor bathroom habits leave decorations on their underpants
Example:
Timmy: Skidmarks!!
Suzie: So you have X-ray eyes and can see inside my pants?
Timmy: No but you smell like poop.
Suzie: Uh, that was you farting. He who smelt it dealt it.
WARNING: These cruel, insensitive and politically incorrect insults are presented for informative purposes only! Do not use in real life, even if your classmates do smell like poop, behave oddly, see poorly or suck up to the teacher.