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

 794

3  

Pull on a coworker is to press ctrl+print screen on their workstation, then paste it into Paint, save the pic, and set it as the desktop background. Move all of their icons to the trash. When they get back to their desk, clicking won't accomplish anything!

 1531

0  

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

 1429

1  

Hide an alarm clock in someone's bedroom and set it for 3:00 a.m.

 775

0  

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

 853

0