Is this a prank?

Calvin had a doctor appointment in Tucson recently. By the time we were done with the appointment it was lunchtime. There are only a couple of fast food places in Tucson that I trust. I've had too many bad experiences to try many new places so we pretty much always go to the Carl's Jr next to Costco. Calvin only likes his cheeseburgers one way, lettuce and mayo. He never varies. Most fast food places do not get it right. With multiple children in the drive-thru I don't always allow them to make special requests but make them eat it the way it comes. It's too confusing to figure out five special orders. This particular day I order Calvin's special for him. I ask for a cheeseburger with just lettuce and mayo. He opens it up and asks, "Is this a prank?" There was no bun. I start laughing and say, "Nope, that's exactly what I ordered." Sorry, I thought the bun was understood, not at Carl's Jr. They are really accommodating to the low-carb crowd. In this case, a little too accommodating.