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

I'm going on an international school trip to Italy 下一个 week(woohooo!!!!!) and there are gonna be some teachers who have been really mean to me some time 以前 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