I always loved to ask a single super obscure question that almost nobody would know the answer to. I didn't expect, or desire the 'correct' answer, I wanted to see how they handled the fact that they were asked something they almost assuredly didn't know. Did they say 'I dunno' and just shrug? Did they make some shit up? Did they try to work it out? That reaction to the uncertain/unknown is, I think, a pretty important part of figuring out if they'll be good to work with - who doesn't run into something unknown on a fairly common basis?