Stern was talking about his new gig as a judge on NBC's "America's Got Talent" and told Letterman how the network told him he'd have to promote the show with appearances on "Today" and "The Tonight Show."
Late-night fans with long memories will remember that Letterman was thought to be a shoo-in for the "Tonight Show" chair when host Johnny Carson retired, only to be passed over for Jay Leno. The ensuing war for late night and the bitterness between Letterman and Leno has now been simmering for decades, and so the loyal Stern refused to go on NBC's rival talk show.
To cheers from the audience, Stern said, "I shot 'em a look and said 'You know I'm a Letterman guy?'"
However, it turned out that Stern felt a bit betrayed by his old pal Dave, as he then found out that "you announced the war is over, I'm still fighting the war!"
For his part, Letterman told Stern, "you're going on that show. I know you're going on that show because they will pressure you and pressure you!" To gales of laughter from Stern and the audience, he then did a hilarious impersonation of Leno telling his audience, "Howard will be here!"
But Stern had to have the last word: "Let me remind you, who did a Super Bowl commercial with Jay Leno and Oprah?" It sure wasn't Stern, that's for sure.
"The Late Show With David Letterman" airs Weeknights at 11:35PM on CBS.
TV Replay scours the vast television landscape to find the most interesting, amusing, and, on a good day, amazing moments, and delivers them right to your browser.
HuffPost Entertainment is your one-stop shop for celebrity news, hilarious late-night bits, industry and awards coverage and more — sent right to your inbox six days a week. Learn more