What are you, nuts?

So - I ride into work today, just like most days. Its ony 7 miles, and its ~20 degrees and dry. I roll up to the door at the office and there are three people having a cigarette, huddled and looking cold. One person, between puffs, says to me....

"What are you - Nuts? Riding a bike in cold weather like this."

I didn't say anything, but sort of gave her a confused look, complete with a slightly tilted head. I swipe my badge, started to head in the door, stopped, and said... "good morning." All three replied in kind.