If you've seen the popular book Elf on the Shelf, it can be a fun tradition. This version even includes a skirt if you want to make your elf a 'she'! Very appropriate for a house full of girls!
Now, if you are an elf-lover, you might get an elf costume to use on those special occasions- like a white elephant party at your mother-in-law's house.
Do you have an elf on the shelf tradition? My mom always had us put our shoes by our door and put oranges in them in the morning. She called it the good fairy, but we were never fooled.