I remember my parent used to tell me when I was a little boy "not to drink when it is getting towards bed time". Reason:"If you do not want your parent dead, because it is an abomination". Actual reason: They do not want me to wet my bed.
My brother in law tell his kids that when the ice cream van plays his music it's to say that he has no ice cream left
Close your eyes and go to sleep or the evil dark figure staring at you from your wardrobe will come out and kill you.
I told my daughter we had a velocoraptor in the shed, as I didn't want her going in there where there was weed-killer, white spirit, etc. Little bastard then tried to get the dog to go in by throwing his toys and treats in.
don't know if you have the ad over there but a kid asks Dad why they built the great wall of china and he replied after a few seconds - to keep the rabbits out