Attempt #1 - (to parent): Please ask your child to stop that.

Attempt #2 - (to child): "Joey, do you like gladiator movies?"

If Attempt #2 is lost on parent, I'll let them know in no uncertain terms that I will be happy to teach Joey (or Jill) the virtues of whiskey, cigarettes, and porn. They can watch Joey age 10 years in one flight or they can put an end to Joey's behavior. I'll be sleeping or entertained.