Still deciding on what joke to pull this April Fools' Day? Sure, you could go with recent favorites like jello-stapler or saran-wrap-toilet-seat, but why not attempt to pull the one truly classic prank: the "Washing of the Lions." 

It's a fairly simple gag, requiring few materials other than some especially gullible targets. Basically, all you have to do is coax a group of people to come to a nearby tower — or other central location — so that they can participate in a special lion-washing ceremony. Later, when they arrive all dressed up and ready to see some big-cat-bathing, you inform them that it was all a hoax, that, of course, there isn't some sort of lion-washing event going on, what kind of crazy idea is that?

Admittedly, this is not an especially funny or clever prank. But its payoff comes in the fact that it is literally the oldest April Fools' joke in the book. Back in 1698, Dawks’s News-Letter reported that “Yesterday being the first of April, several persons were sent to the Tower Ditch to see the Lions washed.” The tower in question was the Tower of London, where there actually was a royal menagerie with lions at that time. There was not, however, any sort of lion-washing, putting the prank in the category of "sleeveless errand" — what today we call a "wild goose chase."

The annual hoax continued well into the 18th and 19th centuries, growing more elaborate even after the tower's lions and other animals were moved to the Regent's Park Zoo. Here's an 1856 invitation to the fake event, held at the made-up "white gate." 

So what are you waiting for? Get out your fancy British stationery and invite your unsuspecting friends to a lion washing extravaganza...for history!