One that comes up now and again...usually after the initial shock of seeing a guy in a kilt subsides:

"How do you go to the bathroom in that thing?"

...now, I didn't say it was an INTELLIGENT question...I just said it was a question.

Best

AA

ps: I've discovered a great answer to "The Question", by the way: no matter what you are or are not wearing underneath, just very casually say "Just matching gym shorts...no big deal." This is SUCH a disappointing answer that the "witty" questioner just lets it drop.