DaveWatch: Countdown to Letterman's Last 'Late Show,' Day 19

Jerry Seinfeld stops by and switches seats, and Jason Isbell and Amanda Shires honor Warren Zevon

David Letterman and Jerry Seinfeld switch spots on Friday's 'Late Show.' Credit: Jeffrey R. Staab/CBS via Getty

"There's one thing that you have never done on this show, [and that] is be a guest," Jerry Seinfeld remarked to David Letterman on Friday's episode of the Late Show. "Would you like to know what that's like?"

So began what will surely go down as one of the most memorable segments from Dave's farewell month, a free-flowing, free-form exchange between the two friends and comedians that was so engaging and effortless, no one would have complained if it had taken up the entire broadcast.

Despite his initial reluctance to cede his desk and take a seat in the guest chair, Dave switched places with Jerry — and was promptly confronted with the intimidating height differential between the two positions. "How am I possibly going to be entertaining with this giant looming to my left?" Dave asked the audience. "Yeah," answered Jerry. "With a bad attitude, also!"

Dave's legendarily crusty attitude was nowhere in sight on Friday night, though. He seemed loose and playful from the get-go, setting the tone for the show with a couple of brilliantly dry jokes about the subway. ("The subways are so crowded now, there's no room for me to breakdance" may be one of the deepest one-liners he's ever delivered.)

His deep affection and appreciation for stage manager Biff Henderson, who's worked with Dave since 1980, was palpable during his intro to a hilarious "greatest hits"-style montage of Biff-related clips. And when Seinfeld — who came out and performed the same stand-up routine he'd done on his Letterman debut in 1982 — turned the tables on Dave and interviewed him, he seemed to eat up every minute of it, even when Jerry was giving him massive shit about retiring.

At Seinfeld's urging, Dave showed him how to do "that run" that he does at the beginning of the show, placed the blame for his impending retirement squarely on his family and revealed that his son Harry's biggest concern was whether or not he'll still be able to watch the Cartoon Network after his dad retires. He was relaxed, funny and maybe the closest thing to "pure Dave" that we've seen in awhile.

Dave also seemed genuinely moved by Jason Isbell and Amanda Shires' lovely, show-ending version of Warren Zevon's "Mutineer." Though their performance certainly succeeded on its own terms, it also evoked the powerful memory of the late Zevon singing it on the October 30, 2002 episode of Late Show, as part of what would be his final public performance before dying of cancer in 2003. Much like the Biff montage and Seinfeld's appearance, the song highlighted the familial thread that's run through Letterman's show since the very beginning. A frequent guest and sometime substitute bandleader on the program, Zevon — who called Letterman "the best friend my music's ever had" — was part of the extended family, which in turn has become part of ours. Friday night's episode reminded us why…and reminded us why we're going to miss it so damn much.