How about some jokes/pranks you have done while at work? This past week i decided to change the desktop on the G4 i use at work the to a picture of the blue screen of death from windows. So i go ahead and do it and just leave it like that. then a few days later this co-worker was like hey i saw your computer and i went ahead and restarted it. and after some closer examination by him he noticed it was just the background image.