A father buys a robot lie detector that slaps people when they lie. He decides to try it for dinner "Son, where were you today?" "At school father" The robot gives a slap on the child. "Ok, I saw a dvd at home Joe's house!" "What dvd?" "Toy Story" The robot takes another slap in the child. "Ok, it was porno"said the  son while crying. "What? When I was your age I did not know what porno was!" Says the father. The robot gives a slap on the parent! The mother laughs "ahahaha! He really is your son" The robot gives a slap on the mother!