I first heard about R in the Princeton math department Common Room, when the head of the graduate admissions committee told a group of us about the students who applied that year. He said that R's application was amazing, with glowing, over-the-top letters of recommendation.
R was incredibly clever. So clever, that whenever I told him about a theorem I had proved, he immediately informed me that my result was trivial and the proof was obvious.
After R became a professor, he invited me to give a seminar talk at his university. I wondered why he had invited me, if he thought that everything I did was trivial. I decided to use the talk as an opportunity to prove to R that I could do something that wasn't obvious. So I chose to talk about a problem a co-author and I had solved where the answer was unexpected. The proof wasn't hard, but it wasn't obvious; it was a little tricky.
During my talk I asked the mathematical question, and before I gave our answer I polled the audience as to their guesses for the answer. The question was whether a certain set associated to an elliptic curve is always infinite, always finite, or whether it depends on the curve, and in that case, with what distribution? Everyone except R ventured a guess. I prodded R to commit to an answer. I wasn't going to let him off the hook. He said he had no idea. When I (rather unfairly) pressed him further, he gave a wrong guess.
At the dinner after the talk, I explained to R that I had noticed that R invariably told me my work was trivial and obvious, and that my talk was a set-up designed to prove to him that not everything I did was trivial.
R told his side of the story, which was that once he understood a proof, even one he had come up with himself, it seemed to him as if it should have always been obvious, and anyone (including himself) to whom it wasn't obvious was just being stupid.
At the end of the dinner, R turned to me and in all seriousness remarked "Now I understand why it's trivial." I burst out laughing. R had thought about the result during the dinner, and now believed it was trivial. I wish I had asked him to elaborate, since he might have found a more conceptual proof, and I would have learned something from it.
While I had always liked R, despite his snap judgments of my work, my feelings towards him got much warmer due to a conversation we had after I moved to Orange County, California. I ran into him at the annual math meeting, and complained about my difficulty adjusting to the SoCal culture. I told him how I had been part of several small social groups for years, and yet some of the people didn't know my name, and the ones who did usually didn't care enough to even say "I noticed you haven't been coming here for the past year. We missed you. I hope everything was OK." They didn't seem to care whether I was alive or dead. In a very heartfelt way, R told me, "If you died, I would care, and it would make me very sad." It was a sweet thing to say, and reminded me that mathematicians, for all our flaws, are a community of people who care about each other.