When someone goes for a pan cracker (poop) find the toilet light switch and wait for a minute.

Now turn the light off wait for the cursing to start grab a cup, fill it with water, throw it over the cubical and run out while closing the door.

Muaha! They won't know who it is and it's a great revenge.

Where I work we do this often and when the lights are out and the doors closed you can't see a *thing*. Not even your finger in front of your eye.