It’s an age-old conversation between husband and wife: “What do you want to eat?”, “Whatever”. It’s a little like when you ask your wife what she’s like for Christmas and she says not to worry about getting her anything. That’s not what she means, and woe betides any husband who takes her at her word.
This guy is going to get in trouble if the pizza place actually does follow his request. I’m almost certain that his girlfriend isn’t going to be happy with an empty box for dinner, nor is she going to see the funny side. But we do!