How One Becomes A Zombie

Patrick, pretending to be a zombie, chases Lizabee around the house for a couple of minutes. Mom asks, "How do you become a zombie?"
He replies, "They dislocate your brain. Wait. Kathryn, how *do* you become a zombie?"
"Oh, they suck your brain out."
"How do they do that?"
"Through your nose."
Lizabee asks, "Oh so they do this while your sleeping?" She proceeds to make sucking noises.
Staring at Lizabee with a most serious face I reply, "They don't put you to sleep."
Wide-eyed Lizabee: "Oh."