A jack-in-the-box is a children's toy that outwardly consists of a box with a crank. When the crank is turned, it plays a melody, often "Pop Goes the Weasel". At the end of the tune there is a "surprise", the lid pops open and a figure, usually a clown or jester, pops out of the box. Some jack-in-the-boxes open at random times when cranked, making the startle even more effective.
A theory as to the origin of the jack-in-the-box is that it comes from the 13th century English prelate Sir John Schorne, who is often pictured holding a boot with a devil in it. According to folklore, he once cast the devil into a boot to protect the village of North Marston in Buckinghamshire. This theory may explain why in French, a jack-in-the-box is called a "diable en boîte" (literally "boxed devil").
The toy gave its name to the fast food restaurant chain Jack in the Box, which features a mascot named "Jack" who resembles a toy clown from a jack-in-the-box.