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Watch then-"Late Night" host David Letterman crash the set of Live at 5 as Sue Simmons, Jack Cafferty and Al Roker were in the middle of a newscast in Studio 6B at 30 Rock.
Long before David Letterman became the host of the "Late Show" on CBS, he roamed the halls of 30 Rockefeller Center as host of "Late Night with David Letterman."
He launched the show on NBC in 1982, taping in Studio 6A, just across the hall from where NBC 4 New York's "Live at 5" taped in Studio 6B (now home to "The Tonight Show Starring Jimmy Fallon").
"Late Night With David Letterman" ended in 1993, after he moved to the "Late Show" at CBS. Letterman announced Thursday he will retire in 2015, after more three decades as a defining fixture of the late night television landscape.
During his time at "Late Night," he enjoyed busting into Studio 6B to visit with Sue Simmons and Jack Caffery on "Live at 5."
Watch more archive video from Letterman's appearances on the "Live at 5" set below.
Letterman's late-night tenure is the longest in TV history. He surpassed Johnny Carson in 2013 at the 31-year mark. Prior to his retirement, Leno had spent 22 years on-air.
-- Gus Rosendale and Colin Bertram contributed to this report.
1982:David Letterman sits down with Jack Cafferty and Sue Simmons to talk about his plans for "Late Night."
1984: David Letterman previews his second anniversary celebration of "Late Night" with Jack Cafferty on "Live at 5."