The little Chinese cook worked at a restaurant, and his boss was very unfair to him - forced him to do a lot of unpaid overtime, do the dirtiest chores, yelled at him for no good reason and generally made his life miserable. So the little Chinese decided to quit, one day just after lunch. He wrote a note and went upstairs to hand it to his boss, but the boss was taking a nap. He wanted to leave a note on the pillow, but the window was open so he feared the draft may blow it away. He found a brick and tied the note to it, and placed the brick on the pillow, next to boss's head. But then he was afraid the boss may wake up on the other side and not see the note at all, so he took the rest of the string that was hanging from the brick, and tied it around his boss's balls. Then he left, assured his message will be delivered. Later, the alarm clock woke the boss up. He reached with his hand to hit the snooze button, and slammed his nose onto the brick. Angry, he threw the brick through the window.

Now why is this a programming joke?

Not really a joke. It happened many times - it's the syndrome of the disgruntled employee. I've heard of guys who have formatted all the archive floppies on their last day, inserted some nasty timebombs in their code, and/or done other sorts of revenge. The most dangerous revenge, though, was when they left everything in perfect order, knowing that the system was powered by one horsepower, and that it won't last when the horse is gone.