One time when I was wheeling my unicycle down the street this manic with a beard and sandals came after me and started asking some really odd questions. Turned out it was Conway and he'd recognised me from the maths common room, so figured I might be able to answer his questions. Turns out I did.
Subsequently I was one of very few people he'd bother playing backgammon with because we'd both play stupidly fast, and switch between extreme style of play, almost at random. I'd usually lose, but he stayed and played because he found it interesting. He's very like a cat, in that he'll play with something for a time, then completely lose interest and walk away without a word.
Fascinating, and humbling, to spend time with someone just so far out of my league.