It's April Fools' Day in Miss Popper's class, and Justine decides to play some funny jokes on her teacher and classmates. Once Justine gets a taste of how much fun it is to play jokes, though, she can't stop. The joking just keeps getting worse and worse. When Justine's friends get tired of it, they decide to play a joke of their own. But will Justine be able to handle a taste of her own medicine?