This is an oldie, but something I will never forget.
I went to Taco Bell back when they first had Chalupas. I thought "Hey, I'll try me one of them Chalupa things!"
Me: I would like a Chalupa with no meat.
Pimply Counter Boy: A chalupa with no meat.
He somberly regarded his cash register for a moment. Apparently there were only buttons for "Beef Chalupa" and "Chicken Chalupa" then a "minus" button.
Pimply Counter Boy: Would you like it without beef, or without chicken?
Me: (stuffing fist in my mouth to keep from shrieking with laughter) What is the difference?
Pimply Counter Boy: (totally serious, of course) Without beef is $1.29. Without chicken is $1.49.
Me: (tears beginning to form, gasping) Well, I guess I will have it without beef.