Growing bored with playing Gorilla.bas, I wrote a program that let out a several second long, <100hz tone, a "Fart" if you will, and then printed "oh, sorry, I couldn't contain myself!".
I backed up autoexec.bat as autoexec.old, wrote a new autoexec that ran my program, deleted it, and then restored the original autoexec.bat to cover its tracks.
We weren't present when it did its thing, but the next day I was informed that if it happened again, I'd lose access, and that was it. No "hacking" accusations or anything.