Lie detector robot

A Man buys a Lie detector robot that slaps people who lie.
He decided to test it at dinner:

Dad: Son where were you today during school hours?
Son: At school (robot slaps son)

Son: Okay I went to the movies!
Dad: Which one?
Son: Harry Potter (robot slaps again!)

Son: Okay I was watching p o r n.
Dad: What? When I was your age I didn't even know what p o r n was! (robot slaps dad)
Mom: hahahahaha! after all he is your Son!(robot slaps Mom)
roflmao........

For some more  short funny jokes