Once (also in JFK) I was quizzed a bit by the CBP officer. I told him I was a math grad student, he said "well, then tell me about the Euler problem". I explained that Euler was a fairly prolific guy, and asked if he could be more specific. He didn't relent, apparently he had seen some documentary that was all about the "Euler problem".

Eventually, we moved on to my background, and I mentioned I had done a masters in computational neuroscience. He said something like "oh neuroscience, my great aunt had that", I think he thought it was an illness? Was sort of expecting the reality TV cameras to be busted out at that point...

He let me through though! Usually I clear immigration in Ireland (one of the few places you can do the immigration before you leave), and those folks are always much more pleasant.