as a kid I would watch the carson tonight show when I could (fridays and vacations) andI was always impressed by ed's ability to chill with whoever. he had a tough gig, to set up Johnny as a straight man, and to converse and make the guests comfortable.
I thought that would have been a pretty sweet gig, and still do.
If letterman needed some wise-ass to sit next to him and set up jokes I would do it in an instant.