Here is a list of some "good clean fun" office pranks that won't get you fired or otherwise outcast.

-Place a small piece of clear tape over the speaker part of the handset and watch the person get annoyed at the caller. For more fun remove the tape for a while then stick it back. Continue this on and off throughout the day.

-Click “Ctrl+Alt+the down arrow” and the display will flip vertically and the mouse controls with it. Impossible to get out of unless you know the shortcut which is the same, but with the up arrow instead.

-Put "Out of service" on all the toilet cubicle doors. Watch all of your colleagues run around. To add to the banter, put signs on the elevator doors as well.

-Sneeze.   Do you have a germaphobe that works with you? This one is a classic. A co-worker pretends to sneeze and sprays water into the air making it look like a cloud of flying germs is landing all over your desk.