When I was in college, the subject of our foreign language final was "describe your ideal boy/girlfriend" (and yes, I did write about an anthro).

Generally, the good professors are the ones that assume you are in their class because you genuinely want to learn and will treat you like adults at work instead of a room full of stupid kids like the ones you left behind in high school.

I also took an advanced biology course in high school once that was pretty colorful. I think, generally, the more advanced the class, the more time the professor can focus on teaching and less on insubordination, and consequently, the more loose and friendly the atmosphere becomes. All that classes I absolutely despised in college were entry level, always because the professor was an absolute prick (minus one, who was an idiot), and I'd swear most of them were that way because they just knew all of us were just there to fill credit requirements and hated us for it.

So honestly, that really doesn't surprise me. You put thirty people in a room and ask them the same question, at least one of them is going to be clever enough to come up with that. And he probably responded quick as he did because it happens at least once a year in that class.