Hmm, I dunno.... things I used to do in Science. Once, when dissecting a heart, I shoved a rubber water pipe into the superior vena cava and watched it spurt out of the aorta when I squeezed it! Fun!
In sceince, on the elementary school, my two friends, twins, did allways big mess. The teacher was so scared of them that she usually punished both of them, even if one was ok.
This happened many years ago, when we returned back to school after having some two beers or so... We were in a laboratory making some experiment. One of the twins wanted to go to the bathroom (because he had serious need because of the beer), but she did not want to let him. So, a bit drunken, caught a Petri's bowl (sort of a glass bulb) and peed into it and then triumphally showed it to the class. Even the second brother sat and behaved totally polite, both get a stricture report to the classbook.