Elf on the Shelf returns every year at the beginning of the Christmas season. He's a mischievous little elf who reports back to Santa Claus every day about children's behavior. The Elf on the Shelf tradition began in 2005 when a mother in California created a Christmas game for her children. The tradition has since grown to become a worldwide phenomenon, with families all over the world adopting their own Elf on the Shelf. The Elf on the Shelf usually arrives on the day after Thanksgiving and leaves on Christmas Eve.