David Letterman on red carpet before he was awarded Mark Twain Prize for humor.

David Letterman on red carpet before he was awarded Mark Twain Prize for humor.

Stories this photo appears in:

Tease photo

'Everything was fine until you went off the air,' Letterman Told as He Receives Twain Prize

David Letterman, the longest-serving host in US late-night television, was awarded the Mark Twain Prize for American Humor on Sunday.