I once had a short chat with Marvin. At our Glendale office several years ago, he was taking a break from his meeting and ventured into our office area. I was playing with a puzzle (see pictures above) and told him that there are to solutions for this puzzle (one in which two heads are aligned, and one in which they are not). As I said "this is like entangled electrons' spin", he immediately responded with a meta question (to the effect of): "Why do these things always come in twos, and not threes or more?, positive, negative, up down?" I could not say much except something like "well, a line has two directions, and..." but that question lingers on in my brain as a sort of question that is philosophical and gives a hint of the world since then. I don't think that he meant this question to be profound, but an answer for a "why" question sometimes leads to more questions.
Alan said that Marvin was a stereo typical "mad scientist"; this short conversation was enough for me to see why he said that.