^A dad buys a lie detector robot which slaps people when they
   lie.
   He decides to test it at dinner. "Son, where were you today?"
   The son says "at school dad." Robot slaps the son!

   "OK, I watched a DVD at my friends house!" "What DVD?" "Toy
   Story." Robot slaps the son again! "OK, it was a porno" cries
   the son.

   "What! When I was your age I didn't know what porn was" says the
   dad. Robot slaps the dad!

   Mom laughs "HaHaHa! He's certainly your son."

   Robot slaps the mom.^