okay..i know this isnt going to be gut-bursting hilarious but we just did this to a friend in april and i was laughing so hard i dont think a bathroom could've looked any better...
first thing you must do is bring the most chicken person you know to the magic kingdom and declare (infront of everyone preferably in the monorail where theres like..zero to no space..) that you are going to cure him/her's fear-problem. if you add one of those obi-wan kenobi "peter pan" hero stances for affect thatd be great. oh, and smile reeeeeaaallllly big at the other guests, so that they can confirm you're out of your bloody mind.
anywho, draaaag them to the haunted mansion. but, seriously, talk to them all therapist like "its okay...the robotic and or holograms wont get you..." even tell them about the hanging mr.gracey in the stretching room. be kiiinnndd. make them looooooooovvvveee you.
then tell them youre not sitting with them. now you can laugh diabolicaly. make them sit alone and tell them to sit to one side, preferably the right, because the left is ALWAYS scarrier. ...okay the left side isnt scarrier but THEY dont know that..its for YOUR advantage. sit infront of them. not behind durnit.
when you exit the attic (you know...the bride..green..lady..) you turn around. so now you are behind her/him. you can laugh diabolicaly again. i did. anyway, reach foreward as faaaaaaar as you can to the now *left* side and scratch/tap/yank on their shoulder and then delight in their piggy-like screams of terror. when you can see them again, happily hum the 'grim grinning ghosts' song while waving like an idiot.
when they yell at you afterwards about "the person" grabbing them, stare at them like they're out of their mind, go ahead and make a scene by stopping dead in your tracks (doorways become your beeeest friend for this situation) and shaking your head. poke them profoundly with the 'i am your master and you will obey' look of doom on your face and declare (loudly. again.) that "I TOLD YOU NOT TO SIT ON THE *LEFT* SIDE!!!!!"
i did this to a friend and its worth acting like an idiot all day long for. try it and if you have a recorder with you, tape them screaming like wilbur from charlottes web.
