A man buys a lie detecting robot that slaps people who lie, and he decides to test it at dinner:
Dad: Son, where were you today during school hours?
Son: At school.
The robot slaps the son.
Son: Ok! I watched a DVD at my mates.
Dad: Which one?
Son: Kung Fu Panda.
The robot slaps the son.
Son: Ok! It was a porno!
Dad: What!?! When I was your age I didn't even know what **** was!
The robot slaps the dad.
Mom: Ha Ha Ha! After all he's your son.
The robot slaps the mom.
Dad: Son, where were you today during school hours?
Son: At school.
The robot slaps the son.
Son: Ok! I watched a DVD at my mates.
Dad: Which one?
Son: Kung Fu Panda.
The robot slaps the son.
Son: Ok! It was a porno!
Dad: What!?! When I was your age I didn't even know what **** was!
The robot slaps the dad.
Mom: Ha Ha Ha! After all he's your son.
The robot slaps the mom.