April Fool's Day

April Fool's Day or All Fools' Day, though not a holiday in its own right, is a notable day celebrated in many countries on April 1. The day is marked by the commission of hoaxes and other practical jokes of varying sophistication, the aim of which is to embarrass the gullible.

Nuisance caused to third parties by April Fools Day

• One type of April Fools Day hoax is to leave a message telling someone to telephone Mr.C.Lion or Mr.L.E.Fant (or various others) at a number that turns out to be a zoo. That prank, repeated across many people, causes serious problems for zoos' telephone exchanges.
• There have been cases when a hoax in a newspaper caused many readers to send mail to a nonexistent address, causing problems to postal sorting offices.