(* I asked the kid to stop kicking, maybe 3 times. I then asked
his father to make him stop. He shrugged it off. I then DEMANDED
he make him stop. He looked at me, and SNARLED! Not sure exactly what he said,
it was along the lines: I can't control him! *)

Mess up your hair and give the kid the "psycho-nerd" look. Cover the dad's view with a pillow so that only the kid sees. The psycho-nerd look is as frighting as any hells angle's snarl.

Snapping a pen in two might add to the effect.

If the dad sleeps, a wayward ice-cube might also do the trick.