Install the Blue Screen of Death screen-saver on someone's computer.

 821

3  

Change the coffee in the office coffee maker to decaf.

 1444

1  

Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.

 891

0  

April doesn't fool Chuck Norris, Chuck Norris fools April.

 843

0  

Put a "Please Use Other Door" sign on the entrance to your office building if it only has one entrance.

 1474

1