Be careful with your lie detector

A dad buys a lie detector robot that slaps people when they lie. He decides to test it at dinner.

"Son, where were you today?"

The son says "... at school dad."
Robot slaps the son!

"Ok, I watched a DVD at my friend’s house!" the son says.

"What DVD?" asks the father.

"Toy story." Robot slaps the son again!

"Ok, it was a porno!" cries the son.

"What?!? When I was your age, I didn't know what porn was," says the dad.
Robot slaps the dad!

Mom laughs "Ha! Ha! Ha! He's certainly your son."
Robot slaps the mom!
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