The first thing i noted was how expert his player skills are. He's fast at everything, pushing the buzzer, speaking the answer, selecting the next clue, calculating his bets. So with his first right answer he controls the board longer, gets more questions in that time, and makes more high-return — really high — Daily Double and Final bets. As for those answers, clearly he has a better memory recall than most of us, and has read, watched and listened widely.
But very few Clues in the game are really outside an ordinary person's common range of exposure. Apart from all pop-culture and sports, when I'm stumped and he isn't, mostly I kinda think I sorta knew that once upon a time, just not now. But always, he has the thing spoken before I even realize, "Hey, that I know".