Favorite April Fool's Joke:
My fourth least favorite boss, Michael, earned that distinction simply for being such a twit. He was gullible to a genuine fault, and even after being told the true information would refuse to believe it, because the true info contradicted what he had heard first, which had to be correct because it was first.
He was not generally respected, and this extended up and down the line, right up the the office manager's secretary, Sandy. So when I suggested the following, Sandy agreed to the prank wholeheartedly.
Michael's schedule put him in the office a full hour before me, supervising the rest of the clerks. In turn, I was pretty much on my own during the last hour, taking care of the clean-up jobs at the end of the day. This particular April Fool's Day, I left him a note, a nice big one, telling him that the office manager had come by to ask Michael a few questions after he had left. No indication about what the questions were about, of course. And, since the manager wouldn't arrive at the office for at least another hour, Michael was left to stew over what the manager had wanted all that time.
When Sandy arrived in the office, she made a point of dropping by the file room, where Michael asked her what the manager had wanted. As we had planned, she replied, "Not to worry, it's already been taken care of." And no matter how much Michael pressed her, she let it go at that.
By the time I arrived in the office, Michael was already climbing the walls, trying to remember what it could have been that was so important! I just kept my mouth shut for a couple of hours, until I finally took pity on the guy and told him the truth. Michael refused to believe that Sandy and I had conspired together on this prank! It took a meeting with the manager to get through to him!