What is the best office prank you have ever seen or participated in for April Fools?

I once conspired with a VP of operations to announce a "re-org" on April fools day. The re-org was "in an attempt to facilitate cross-training and help everyone get a better view of operations".

The new Org chart was great! Several managers and their direct reports were reassigned to areas in which they had no experience or expertise. Helpdesk techs were going to be managing facilities and the facilities guys were going to take over senior engineering and architecture.

It made for some great laughs but we never actually got approval from HR to send the notice. :(

I can't remember if it was for April Fool's day, but there was one day where a few of us saran-wrapped every object on a coworker's desk... and then saran wrapped the entire desk! Juvenile? Absolutely, but the look on his face was priceless.

We filled 500 styrofoam cups 1/2 full with water starting from the back of the "NEW" bosses office, moving forward to the entry door. Put them 2" apart including under the desk, on the desk and behind the door. The next day we filled the entire office with a months worth of industrial sized paper shredding. Welcome to working at a highschool.

I just talked to my friend that did the other prank. He said that this year he's planning on doing a jello keyboard and mouse prank. I ended up googling it and found this: http://www.hemmy.net/2008/05/27/jelly-keyboard-mouse-prank/

Some years back, I had an April 1st prank played on me and, in the spriti of the season the next year decided to play one on the perpitrator. I wrote a small application that would periodically (based upon both keystorkes and mouse movements) take an image of whatever was on the monitor and then it would display that fixed image instead of and on top of the actual monitor's various windows. (This would simulate the keyboard and mouse suddently becoming useless. ;-) The fixed image would remain on top until either a certain key store combination (something like ) was used to "release" it or for a period of 5 to 20 seconds, at which time the image would revert to whatever was actually being worked on.

This worked like a champ to frustrate my adversary for the whole day. He spent a great deal of time trying to resolve this "intermittent problem" on his own and with the assistance of the Help Desk (who, by the way decided he was either messing with them or just a little crazy).

The next day I told him what "intermittent problem" was and we joined forces to add a Keyboard Error message, a Mouse Error Message, and a "Communications Error Message" to the application and to drop it on another co-worker's machine on that person's birthday. ;-)