My team mates know that I will use almost every opportunity to remind them that leaving your computer unlocked when I'm around is not the best idea. Most of the time I try to perform some harmless prank like reconfiguring the screen to be rotated by 90 degrees or set embarassing wallpaper. It happened many times but they never learn ...

But if they see me near their keyboard, they run in panic! Given that my daily job is developing automation software I was wondering if there is any way to speed up or even fully automate process of getting your collagues embarassed.

I present you with Teensy Pranker. The idea is simple - your victim forgets to lock the computer, you plug in earlier prepared teensy microcontroller into their USB port and within just few seconds wallpaper will be changed to very nice picture of pink pony. This particular version works with standard OSX, but the code is really easy and can be modified for anything else.

DISCLAIMER: I was joking, don't use it on anyone's computer. Just your own. Playing with someone elses computer without their consent can get you in serious trouble.

Inspired by samy's usbdriveby.