If bạn could prank your teacher, what would bạn do?

I'm going on an international school trip to Italy tiếp theo week(woohooo!!!!!) and there are gonna be some teachers who have been really mean to me some time cách đây but I've never gotten them back.

So, does anyone have any good pranks against teachers? No scare pranks, please, I already have tons of those ready >;3