Did you play a joke or have one done unto you? Find a cool website gag?
Just cheesey things at work so far for me. The radio station which we have piped in keeps spam playing the rick roll song.
One lady brought in cinnamon rolls for everyone to eat...but we soon found out they were plastic
Somebody came in and put post it notes on the bottom of our laser mice.
One lady who transcribes chart notes for me, every morning I give her a big plastic envelope of them. She always has an over dramatic spazz out if its a lot to do. So I took the envelope and shoved it as full as it could go with scrap paper and put just 1 real paper on top to make her think it was all real. She predictably had a near heart attack believing it was all work for her to do. Heehee.
Oh yeah one last thing I forgot. This one portal we have to use, has a captya system (or however its spelled). The web team for it put up a fake one using chinese kanji. If you actually clicked on it to type it took you to the real thing.