Elf on the Shelf has been around since the early 2000s, when the tradition of placing a special elf in the home was popularized by the bestselling children's book "Elf on the Shelf: A Christmas Tradition." The tradition has become a popular holiday tradition for families, with parents placing the elf in different locations each night during the holiday season to keep an eye on their children's behavior. Elf on the Shelf is also a popular theme for decorations, clothing, and toys, and the tradition has been expanded to other holidays such as Halloween and Easter.