The first story comes from an old admin I worked with. Apparently he worked for a hospital as a helpdesk person and received a call from one of the higher ups. The issue expressed over the phone was a request for a larger mouse pad as he kept running out of room. When he heard this, he shook his head and decided to take a walk up to the office to find out what was going on, When he got there and looked in the door, he had to turn around and walk away, because he was laughing so hard. The executive would use his mouse and hit the end of the mouse pad. Instead of picking the mouse up, pulling it back and then moving the mouse again, he would pick the mouse up, slide the mouse pad forward, set the mouse down and then move it. Anytime it hit the edge of the pad, he would do the same thing.
The next story comes from my old beowulf days. I was working for a company as an admin. They staff were programmers that designed DSL Modem Processors and the software that run on them. One day another admin and myself decided to play a prank on the staff. I remebered a tool that we used when creating beowulf clusters that would allow me to issue a command to multiple machines at once. We used it for configuration. Well, it is also good for ejecting cd-roms. We loaded up an inventory of machines and typed eject cdrom. Its amazing the sound of 35-40 cdroms drives opening at the same time. It's even more funny when you hear the expressions of 35-40 staffers saying "WTF?"