And the feud goes on.

David Letterman and Jay Leno have been locked in a highly publicized rivalry for two decades now -- ever since Leno was named Johnny Carson's Tonight Show replacement over Letterman, who left NBC for CBS as a result of the snub. The battle between the two comedians is so famous that it was the subject of a 1996 HBO film, The Late Shift. But Letterman claims that their fallout is more complicated than some 20-year-old spat over a job.

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In a new teaser for his sit-down with frenemy Oprah Winfrey -- with whom he had a 16-year feud beginning in 1989 -- Leno's rival opens up about his much-discussed relationship with his fellow comic and former pal. (The full Oprah's Next Chapter interview airs Jan. 6 on OWN.)

"We were always friends before all of this happened," the Late Show host, 65, tells Winfrey. "He has a way...he's an unusual fellow. I've never met anyone quite like Jay."

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He goes on to add that despite their feud, he thinks Leno is "the funniest guy" he's ever known. "If you go to see him do his nightclub act, [he's] just the funniest, the smartest, a wonderful observationist, and very appealing as a comic," Letterman says.

High praise -- but there's a "but."

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"Therefore, the fact that he is also maybe the most insecure person I have ever known...I could never reconcile that," the comic says.

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This article originally appeared on David Letterman: Jay Leno Is "the Most Insecure Person I Have Ever Known"