80's or 90's boy cuts off a fake hand with a mini guillotine

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I don't have many details on this one, it's just a scene I recall seeing while flipping channels a while back. I don't know if this was a movie or an episode of a TV show. It was likely from the 80's or 90's and there is a boy who has a mini guillotine. I believe the scene was at a kitchen table. He was showing it to someone and then seemingly put his hand in and cut it off. This made the other person freak out until the boy revealed that it was a fake hand.