On May 23, 1991, Johnny Carson confirmed rumors that had been swirling at the time and announced at an NBC network affiliate managers meeting that he would be retiring from The Tonight Show Starring Johnny Carson at age 65 the following year, ending his 30-year run as the host that defined late-night television for generations.
That evening, he made this surprise appearance on Late Night with David Letterman and off-handedly made the same announcement to the public at large. Letterman told Carson that he carried the NBC network for years, and Carson demurred. "It's coming to an end next year," Carson replied, before quipping "I've always wanted to be a shepherd."
Carson also made a fantastic and brutal joke at the expense of NBC's then-owners, who Letterman famously mocked with regularity. "A lot of people have said General Electric is not interested in being in the entertainment business... I saw the fall schedule, and there's nothing to worry about."
Andy Hunsaker has a head full of sitcom gags and nerd-genre lore, and can be followed @AndyHunsaker if you're into that sort of thing.