A man buys a lie detector robot which slaps people who lie. He decides to test it out at dinner with his family.
Dad: Son, where were you today during school hours?
Son: At school. [robot slaps son}
Son: Ok, I lied. I went to see a movie.
Dad: Which movie?
Son: Toy Story. [robot slaps son]
Son: Ok! It was porn!
Dad: What??? When I was your age, I didn't even know what porn was! [robot slaps dad]
Mom: Forgive him, dear. After all, he is your son. [robot slaps mom]