1. The Jello

This one is simple: put your coworkers things into jello.
2. The Hidden Cellphone
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For this one, all you have to do is hide your coworker cellphone and then start calling nonstop.
3. The Gift Wrapped Fake Desk
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This one is a little more tricky. But if you have patience, all you have to do is create a fake desk and then wrap it like a christmas gift.
4. The Morse Code
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For this one you'll need a office buddy. You two can learn morse code to talk about the other coworkers in front of them.
5. The Desk In The Bathroom

You have two options for this one: Or you stay late at work to change your coworker desk to the bathroom or you can get a little earlier to do this.
6. The Impersonation
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Just dress exactly like your most annoying coworker and impersonate him until he go nuts.
7. The Vending Machine

If you're friends with the vending machine guy this one will be a piece of cake for you. Grab all of your annoying coworker stuff from his desk and put it in the vending machine.
8. The Faxes From The Future
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Make your coworkers believe that they're receiveing messages from they're future selves.
9. The Michael Jackson
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The traditional call prank pretending to be Michael Jackson.
10. The Snowman Army

Create a snowman army in the parking lot to terrorize your coworkers.