The usual suspects.
When I was in grade one, some of my classmates and I returned from recess to find a big puddle of pee in the middle of the classroom.
Our teacher herded us into the hallway and unveiled her brilliant plan: she would let us into the classroom, one student at a time, five minutes apiece. Under her proposal, the guilty party would clean up the puddle with paper towels and the crime would remain anonymous. Truly, a win-win.
So, one by one we took our turn in the classroom. At the end of the onerous process, we walked back into the classroom together, and there we found - TWO puddles of pee.
The moral of the story? I have no idea, but I swear: I didn't do it.