http://www.linuxloop.com/news/2008/11/29/5-pranks-for-your-linux-using-friend/
5 Pranks for Your Linux-Using Friend 1. Set XKill to start when the user logs in Go to System > Preferences > Sessions and add an entry with the command 'xkill'. If you have not used xkill before, it turns your cursor into an 'x' (may vary by distribution) and kills the process behind the next thing you click on. Watch out with this one! Using this on unsaved work would be very bad. 2. Change/remove main menu shortcuts Go to System > Preferences > Main Menu. Then either just uncheck any boxes you want or switch the command associated with the application shortcuts around. Either way, the recipient of this prank will have no idea how to get their programs to launch. (You can also set one of them to the command 'xkill' described above. This is probably not a good idea, though, since it is very possible that the user would accidentally click on something they shouldn't. In short, be careful and don't do it.) 3. Replace desktop background with a picture of the desktop This trick will work on any OS, but it is still one of my favorites. Just take a screenshot of the computer's desktop without any windows open. Then set that screenshot as their desktop background. Just move some or all of the desktop icons to another folder (be sure you don't delete them) and watch as the computer's user tries to click on his/her icons without any luck. 4. Change the terminal's colors Know a geek who loves to use the terminal? Open terminal and go to Edit > Profiles. Then choose to edit the default profile and mess with the colors. For maximum confusion, leave the background color, but change the text color to match it. Be careful you write down the previous settings, though, if the user has changed them. 5. Free the fish When you walk by the person's computer, simply press Alt+F2 and type in "free the fish". This will cause a fish you swim across the desktop over and over again. You will have to do it again after every reboot, though. -- "As we open our newspapers or watch our television screens, we seem to be continually assaulted by the fruits of Mankind's stupidity." -Roger Penrose
