The question I didn't get to ask:

Does Tony Mendez still speak Spanish?

Every once in a while, Letterman would say something about Spanish or Cubans, and his cue card guy Tony Mendez would start screaming in Spanish and stomp off the show. I hadn't seen them do this in a while, and this struck me as the typical kind of absurd question that Letterman would like. It turns out that just the week before, they did that stunt again, so my question wouldn't have been that good anyway.