(Standing in a long line at the grocery store waiting to check out. The guy in front of me was holding a case of Anchor Steam beer. He glanced back at me, and I smiled.)
Him (sort of sheepishly): "I never come to the store and just buy a case of beer and that's it. Today's an exception."
Me (glancing down at the basket I was holding): "Well, I never come to the store and buy four cans of biscuit dough, but today's an exception for that, too."
Him: "Right on."