Hell, half the registry tweaks at
http://registry.winguides.com/ can be used to play pranks.
One of the other platoon leaders at my national guard unit has a Prince Albert. My platoon sergeant at the time had a laptop that was also used by his family while at home.
So I took a picture of my friend's pierced prick, set it as my PSG's wallpaper, and did several registry hacks to prevent him from changing or deleting it.
Needless to say, he was pissed, but fun at other people's expense is the whole point of pranks.
