The "Elf on the Shelf" is a Christmas tradition that originated in Germany in the early 1900s. The elf is a small figurine of an elf that sits on a shelf, keeping an eye on children's behavior leading up to Christmas. On Christmas Eve, the elf flies back to the North Pole to tell Santa if the children have been naughty or nice. Many families now use this tradition to encourage their children to behave well during the holidays, and the elf has become a beloved part of the Christmas season.