Interesting idea.

I'm definately going to do that when I graduate, after I try to pull off a nice little prank I read.

Take 3 pigs (there are alot of them around here, in fact I could probably borrom them from my friends dad who's a pig farmer) and paint the numbers 1, 2, and 4 on them and leave a note on the office saying "I have realeased 4 pigs into the school, good luck finding them). Of course they will eventually find the 3 pigs, but will keep looking for the missing number 3.