Throw a package of fleas on them
These can be ordered online or through a pet store. Watch the look of horror on his face when he realizes what you have done!! Then sit back and giggle as they dance around scratching incessantly!!

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Pour Marshmallow Fluff on em'
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Dull ever razor in his house, make sure to nick the blades a bit.
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Put Nair in all his shampoo bottles.
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Shred fiberglass pink insulation all over his clothes.
Think this itches when you touch it? Try having it embedded in your hair!! This plus the fleas... he'd be scratching for weeks.
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Press chewed gum into his face
Make sure to work it in really good!
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Throw deer urine on him.
This would stink for days!! It can be purchased easily through any hunting supply store.
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Get him drunk, shave his eyebrows off :)
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Wrap duct tape around his face
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Stick him in a room with a Mime
And be mean with this one, make sure the room is locked and it's a really awful mime.. not that there is such a thing as a GOOD one to start with.
Hell, lock the rabid, mean ass dogs in there too!!
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OnMyList
List your pants off!