My Thurston memory

My first tenure-track job interview was at Cornell.  During and after my job talk, most people were pretty quiet, but there was one guy who kept asking very penetrating and insightful questions.  And it was very confusing, because I knew all the number theorists at Cornell, and I had no idea who this guy was, or how it was that he obviously understood my talk better than anybody else in the room, possibly including me.