The 79-year-old former host of NBC's "The Tonight Show" occasionally sends [David Letterman] new jokes he has written and that Letterman sometimes uses in his nightly "Late Show" monologue, according to CBS senior vice president Peter Lassally, a onetime producer for both men.

[Johnny Carson] retired in 1992 after nearly 30 years as host of "The Tonight Show" and was replaced by Jay Leno. But Carson has always felt privately that Letterman, not Leno, was his rightful successor, Lassally said.