"Our next guest is one of the greatest quarterbacks in college football and is a favorite to win the Heisman trophy on Saturday. Ladies and gentlemen, from the University of Tennessee, please welcome No. 16, Peyton Manning."
You could kind of just tell.
Watching David Letterman for all those years — and we'll all watch him tonight, for the last time — you could tell those rare instances when he's more excited to see a guest than even the guest was to see him. For most celebs, even those who walked off the red carpet and onto his stage, being on Letterman seems humbling.