Some people call this All Fool's Day. For hundreds of years the first day of April has been the day to play practical jokes on people.
Some kids spend weeks thinking up the perfect joke.
April Fool's Day is an ancient celebration, but no one is quite sure how it started. It may go back to the ancient Roman festival of Hilaria, part of which was a spring fun festival. Everybody is allowed to do very silly things on April Fool's Day, but only in the morning. April Fool's gone past, You're the biggest fool at last. When April Fool comes again You'll be the biggest fool then.