What are some office pranks you've seen pulled on coworkers?

On The Office (US version) Jim is always doing things to Dwight, like sending him faxes from "Future Dwight," or putting his office supplies in Jello. One time at my office someone put a fart machine under a chair in a conference room and would make it fart quietly during meetings, which would make the person in the chair look guilty and everyone else would have to act like they didn't hear anything.

What are some things you've seen?

friend of mine worked in an office with cubicles. the night before april fool's day, some of his co-workers put packaging tape across the front of his cubicle and filled the entire thing with packing peanuts! To this day, I still don't know where they got all the peanuts

I've seen people leave their email open, and someone sent everyone an email requesting money for a sex change.

I had a co-worker asked me if I liked heavy metal in the 80's so when I said yes I found myself standing at the subway with my hands in my coat and pockets full of paper clips and a note that said - here's some heavy metal for you to enjoy

I don't work in an office, I work in a hospital kitchen and the other day two guys set up another guy to get all wet. They went over to the sink where this guy would be working the next day and positioned the sprayer to spray him when he turned on the main valve. I don't know if it worked or not. The guy never said anything and I can't ask him without him knowing that I knew about it.

One of the things I've done is when I had to deal with a co-worker who spend most of her time in the cafeteria drinking coffee. With the help of a few other office criminals, we were able to get inside one night, and we took everything in her office - desk, chair, computer, right down to the last paperclip and rubber band - and set it all up in a corner of the cafeteria.

The CEO was not pleased.

I've put a guys hand in a blender. I don't think he thought it as funny as I thought it was, though.