I love a great practical joke, but I don't know that I've ever seen one to top this.
On Saturday, Kyle Kendrick, Philadelphia Phillies pitcher was called into the Phillies' General Managers office, and was told that he'd been traded to a Japanese team-the Yomiuri Giants-for a Japanese pitcher, Kobayashi Iwamura. The entire team management was in on the prank, as were a slough of newsmen, who were onsite for the fake news conference.
The incredible thing is that Kendrick signed the trade paperwork without even attempting to contact his agent.
It's a great prank, and fun to watch.