These didn't happen the last day, but they happened in high school and were funny.
1) Freshman year, we had this friend we called Schmiles Schmoen and he had really long hair. We told another friend to slide a greasy corndog up his neck and he did. This resulted in a chase around Russelville (the library) and the corndog getting smashed and ground into the Russelville carpet. The librarian came and demanded, "WHO DID THIS?" and they both pointed to another innocent guy, my friend Carl, sitting in the distant corner. He had to clean the mess up. Ha ha!
2) We were all sitting around in Russelville, talking loudly I guess, and a librarian said, "If you want to scream, do it outside." Carl said, "open a window" and someone did. He then went outside the window and yelled a nightmarish banshee scream. It was the best scream I've ever heard, and it was worth having the librarian come down and talk to us innocent people at the table again.
"All this guy ever does is eat, sleep, say stuff, DDR, and wear glasses."