The Lie Detecting Robot

A man buys a lie detecting robot that slaps people when they lie. So he decides to test it out at dinner...
Man- "Son, where were you today?"
Son- "At school."
Robot- *SLAP*
Son- "Ok, I was at the movies!"
Man- "What did you see?"
Son- "Toy Story 3"
Robot- *SLAP*
Son- Ok, it was A Day With a Porn Star!"
Man- "What!? When I was your age, I didn't know what porn was!"
Robot- *SLAP*
Mom- "HAHA! Well, he is your son!"
Robot- *SLAP*

Hope you liked!