A man buys a lie detector robot which slaps people who lie. He decides 2 test it at dinner.
DAD: Son, where were you today during school hours?
SON: at School. Robot slaps son! Ok, I lied, I went to the movies.
DAD: Which one?
SON: Toy Story. Robot slaps son again! Ok, it was a day with a pornstar.
DAD: What?! When I was your age, I didn't even know what porn was..Robot
MOM: Ha ha! After all he's your son. Robot slaps mom..