Attach an air horn to the toilet wall while you're hiding to give unsuspecting people - and everyone else in the toilets - a shock when they open the door.
Obviously DON'T do this to anybody with a heart condition or amazing reflexes. That'll just end with you getting a black eye.
Hahahaha! I think that's too harsh my friend. My mother would kill me if I do this to her LOL!
hahaha for sure