there was a robot,

whenever someone told a lie that robot would slap them.

so a family bought one of these robots, the son came home and the dad asked him
"why are you so late"
the son replied "i was in the library studying"
SMAAACK - the robot hit him for lying

so the dad said, "see tell the truth where were you"
the son replied "i was clubbing"
the dad knew he had his son in a awkward position, so he took advantage and asked further Qs

"have you got a girlfriend"
son replies "no"
SMAAACK

"did you take money out of my wallet"
son replies "no"
SMAAACK

the dad really frustated shouts out to the mother

"this robot has helped us find the truth out, look at your son he has been tellin us all these lies, you have spoiled him, its your fault he is like this"

the mother angrily says "well you say somethin to him as well he is your son as well"

the robot turned around and SMAACKED the mother