1) Arrange with other co-workers to bring in changes of clothing and throughout Friday, change, and baffle the staff.

2) Take the tracker ball out of a co-workers mouse for some fun frustration.

3) Photocopy a paperclip onto a few pieces of paper, put them in the machine, sit back and smile at the wonder.

4) If you have access to it, re-create the office phone extension list for the day, fun, fun, fun.

5) And finally,  a smirk will work. "Did you enjoy your coffee?" "Just wait until you check out the fridge" Follow these with a smirk all the while you've done nothing to either and you'll keep them guessing.

Also, enjoy this prank that's been a big hit on YouTube for a while. There may be an expletive at the end, it's unauditable to me.