I wonder if Dave pays him?

Johnny Carson Writes Jokes for Letterman
LOS ANGELES (Reuters) – CBS “Late Show” host David Letterman has a secret joke writer — and it’s none other than the retired king of all late-night television, Johnny Carson.
CBS senior vice president Peter Lassally, a onetime producer for both men, said on Tuesday that the 79-year-old former host of NBC’s “The Tonight Show” occasionally sends Letterman new jokes he has written and that Letterman sometimes incorporates them into his nightly “Late Show” monologue.
Lassally, appearing at CBS’s annual winter showcase for television critics, said that while Carson has remained out of the public eye since retiring, he keeps up with late-night TV, as well as with political news and other current events that were once fodder for his own “Tonight Show” monologue.
“I think the thing he misses the most is the monologue,” Lassally said of his former boss. “He reads the newspaper every day and might think up five good jokes that he wishes he had an outlet for. Once in a while he sends jokes to Letterman and Letterman will use his jokes in the (‘Late Show’) monologue and he gets a big kick out of that.”
Carson retired in 1992 after nearly 30 years as host of “The Tonight Show” on NBC and was replaced by Jay Leno. But Carson has always felt privately that Letterman, not Leno, was his rightful successor, Lassally said.
Letterman, who long hosted NBC’s “Late Night” show immediately following Carson’s program, jumped to CBS in 1993 in the flagship 11:30 p.m. time slot opposite Leno, setting up one of the most storied rivalries on U.S. television.
While Letterman’s New York-based CBS show initially drew bigger audiences than Leno, NBC’s “Tonight Show” shot in Burbank, California, eventually settled in as No. 1 in viewership, although Letterman has enjoyed improved ratings this season.
CBS Chairman Leslie Moonves said “Late Show” ratings are up 7 percent over last year, marking Letterman’s most competitive position against Leno since 1994 and narrowing his audience gap to just 1 million viewers fewer than “The Tonight Show” versus 2 million a year ago.
Carson, who has lived in relative seclusion in Malibu, California for the past decade, has battled emphysema in recent years, but is “still interested in literature and politics and all the worldly things that he was always interested in,” Lassally said.