One day I decided to mess with the egotistical teen teacher. I wrote a little TC++ program that ran from autoexec.bat. On bootup, it put out several seconds of a low frequency buzz from the PC speaker and then printed "Oh, Excuse me! I couldn't contain myself!" and then disappeared. At that point, the autoexec.bat removed the binary and then overwrite the old autoexec.bat over itself, removing any proof.
Nobody could say it was me, but the Librarian knew and said if I did it again I wouldn't be able to go back. But she also said he was really pissed by it and I get the feeling she got a kick out of it, too.