No joke: David Letterman yukked it up on late-night TV longer than anyone else.
Now his career of comedy has earned him a prestigious award and a celebrity roasting in Washington, DC.
Letterman was to receive the Mark Twain Prize for American Humor during a star-studded celebration Sunday night at Washington's Kennedy Center.
Expected to attend are previous recipients Steve Martin and Bill Murray, late-night host Jimmy Kimmel, musician Eddie Vedder of Pearl Jam and Al Franken, the comedian-turned-senator.
The 70-year-old Letterman spent 33 years on late-night TV, hosting long-running shows on NBC and then on CBS. His final broadcast on May 20, 2015, was episode No. 6028 that Letterman hosted. It shattered the record of his mentor, Johnny Carson.
(AP contributed to this article)