Need something to help keep the kids in line, since you don't have access to Satan, Hell, or even the milder "making Baby Jesus cry?".
Steve Loughran has the answer: Cthulu for three year olds.
I especially liked the caveat, though:
The hard part is striving a line between providing the minimum of lies necessary for total obedience, without reducing the child to having a deep fear of darkness, docksides, attics, cellars and the wind rattling the shutters.