Backpack is a nasty prank that will take only a moment or two to install and give you a lifetime of story telling afterwards. First, download it and open it up. You have 4 screen pictures that you can install as the computer’s desktop picture. Follow the directions included and install it while your victim is away from the computer.
When they return, just wait for their scared reaction.
You’ll like this one!
To EXIT just change the desktop properties.