27 Surprising Things You Don't Know About the Elf on the Shelf, Straight From the Creator

Each elf and elf pet doesn't first receive his or her Christmas magic until they are adopted by a family and given a name. This magic is what allows an elf to fly to the North Pole each night to tell Santa Claus about all of the day's adventures or a reindeer to grow full-size and help pull Santa's sleigh. Elves and reindeer all hibernate until they are given a name.