ooo, have an area that is dark or blindfold the kids to go through your "Laboratory". have a bowls full of Brains (spaghetti noodles), eyeballs (Peeled grapes), and other squishy things (worms etc). Let the kids put their hands in the bowls without looking/seeing what's actually in there. Get lots of squishy things - noodles, pudding, jello, grapes, fruits, peas, etc.
My uncle also made a meatloaf in the shape of a person with spaghetti inside the head for brains, cheese sticks for bones, ketchup for blood. So from the outside, it just looked like a person, but then you start hacking into it and get all sorts of surprises :)
for food, serve the man-meatloaf, gummy worms, eyeballs (Olives), bones dipped in blood (Cheese dipped in marinara), boogers (stirred up jello), spider webs (cotton candy), bugs (raisins)