Late night on the 31st I figured I had to do something to prank someone, anyone, at work. So, I IMd my CTO and suggested that I lock everyone out of the time management system (which most people would use every morning), with a note like:

"Sorry, this account has been disabled. Please contact [CTO name] unless he has already set up a phone conversation with you."

He liked the idea, so at 9am on the 1st, that's what I did. You'd log in, or hit any page once logged in, and see that message. He then took it a step further. After a while, he sent out an email to the company. It said, something to the effect of, 'You have likely noticed you've been locked out of the time system. Please see this blog post for an explanation...." Then it went to an (internal) blog saying we had been bought out, he didn't know about everyones job, etc... Finally, with a link at the bottom to a press release, which really said "April Fools" when you clicked on it.

This would work if two things happened. First, someone forgot it was April 1st. Second, if they didn't click on the PR link. Both happened :-) Some people were pretty freaked out, and the prank went off pretty well.

The best thing about it, is that people want to get him back! I'm just a silent partner in it.