How can you make people look bad (in puplic or not)? Please answer it doesnt mater what it is !! :-)?

Okay here's the deal, we are a couple of girls that are dealing with some annoying boys that always have to comment on EVERYTHING! Like once we were at school and my friend was picking something up from the floor and got a "plumber" (I don't know how to spell it) and one of the boys took it up on video on his phone and showed it to the whole school! And another time the boys were in some game and one of them was dared to ask my friend to be his girlfriend, my friend (the girl) had a big crush on him so of course she said yes, but he was just joking and "dumped" her after like an hour and she was soooooo pissed and I think she lost her crush there... So yes we are looking for some atvise how we can do something back to them...we had an idea of painting on there faces if they would fall asleep at work but we think that's going to be kinda hard cause there always so crazy they are NEVER still! So we NEED some ideas how we can do a prank on them or something mean. :-)