Instead of scaring my youngest girl about the Boogie Man coming to get her if she's acting like a real PITA, I tell her the Beetus will come for her.  Then I use my wife's phone to show her pictures of fat people that have had toes, feet, and legs amputated.     Just kidding.  I don't tell her the Boogie Man or Beetus will get her for acting out.  I let her know the Boogie Man is made up and the Beetus will get her if she gets fat. (I don't, but now I'm tempted as she's a first grader and can understand fat is not healthy.)