Tell a younger sibling that if you squeeze a ketchup packet, really hard, it will turn green. They will squeeze and squeeze and watching them squeeze is just a quarter of the laughter. When it explodes into a red ketchup mess watch your victim scream and burst into laughter. Be on your best prank alert though, as they're bound to tell your parents or get you back.
You take a shoe box or any box out of use, and cut a hole through the bottom of the box so your hand can fit through, then you decorate the box nicely, once you have done this it's ready to show! You put your hand through the hole and tell them to lift up the lid and surprise them with the contents!
You take a bar of cream cheese and a spoon then you get their deodorant and role it down or take the deo stick out completely and replace it with the cream cheese. When he puts on deodorant he will be surprised by the mushy stuff under his armpits and it truly does not smell great either!