Weirdest offerings served in a McDonald's or other fast food restaurant?
In any fast food restaurant: Anything in the "Heart Attack Grill" in Las Vegas, which is dedicated to excess (Stuff fried in lard, butter in milkshakes, and extra beef patties in burgers.)
In a McDonald's: I guess that burger with a pitch black bun served in Japan. (Halloween special) Or the Tiki Aloo (Potato Patty) Burger served in India.