Back in Highschool I used to telnet into all of the HP Laser Jet 4050 printers and disable all printing. Then in computer class we'd have an excuse to do nothing since we couldn't print out our work. It usually took the IT guys about 35-40 minutes to fix it each time, when all that really needed to be done was to shut it off for a second and turn it back on.

LoL @ them.