Me, in complete shock on the inside but attempting calm, cool, and collected on the outside: "Um, what's the F word?"
(Praying now, please Lord, let it not be so!)
Elbow: "I can't say, it's too bad."
Me: "Well, I should know at least, so I don't use it."
Elbow: "Fine. It's 'Fairies aren't real.'"
Me, breathing again: "Oh, that is bad."