I've always been scared of that McRib sandwhich...
it just creeps me out for some reason...is it meat? is it really a rib?...does it occur naturally inside a cow?
It skeeves me out a little bit too, but it's so good.
The ingredients for most of their burgers say like "Quarter Pound 100% Beef Patty" or whatever, but for the McRib and the McChicken it just says "McChicken Patty" or "Pork McRib Patty".

Not real reassuring.
ETA: Just found the ingredients for McRib patties and McChicken patties!
McRib patty: Pork, water, salt, dextrose, BHA and BHT and propyl gallate and citric acid (preservatives).
McChicken patty: Chicken, water, salt, sodium phosphates. bleached wheat four, water, wheat flour, food starch-modified, salt, spices, partially hydrogenated soybean oil and cottonseed oil with mono -and diglycerides, egg whites, wheat gluten, paprika, dextrose, leavening (sodium acid pyrophosphate, baking soda, monocalcium phosphate, ammonium bicarbonate), garlic powder, yeast, natural flavor (plant source), extractives of paprika. Prepared in vegetable oil (Canola oil, corn oil, soybean oil, hydrogenated soybean oil with TBHQ and citric acid added to preserve freshness). Dimethylpolysiloxane added as an antifoaming agent.
Yikes.