It was hard to think of what exactly ought to go into a noxious Noxious Potion. Surely things that smelled, although perhaps that was a bit obvious. "Socks. Really stinky socks," Mo muttered, although that wasn't a real answer and he hoped she wouldn't count it. Just a for pretend answer, see?

"Maybe mustard seeds or oil, Professor? As far as mundane plants go, there aren't many that are more irritating to eyes, skin, and the smell..." He waved his hands. It burned out your nose hair, that much was for sure.