On the show, people in the audience are often wearing coats, or appear "bundled up". This is because the temperature of the Ed Sullivan Theatre is kept at 58 degrees during taping, supposedly at Dave's insistence.
Before reading the Top Ten List, David Letterman used to announce that it came "from the home office of Sioux City, Iowa". This was a reference to the fact that at the time, the CBS affiliate in Sioux City refused to air the show.
In the wake of the September 11, 2001 attacks (specifically the World Trade Center attack in New York, downtown from where "The Late Show" is taped), David Letterman was reported to have said that he didn't know if anything would ever be funny again. Most American programming (including "The Late Show") was suspended in the aftermath. However, on September 17, "The Late Show" was one of the first comedy shows to resume regular programming. The starting guest that night was Dan Rather, and the emotionally-charged episode is considered one of Letterman's finest.
One of the series' most memorable moments occurred in the mid-1990s when Johnny Carson made a surprise walk-on appearance. David Letterman stood up and let Carson sit at his desk for a moment, with the intent of having the The Tonight Show Starring Johnny Carson (1962) veteran deliver a joke. The audience went crazy and applauded for so long that Carson never got to say a word.
Many, including rival talk show host Jay Leno, whom NBC chose over David Letterman as Johnny Carson's The Tonight Show (1962) successor in a bitter competition between the two, saw Carson's Late Show with David Letterman (1992) cameo appearance as a signal that Carson preferred Letterman over Jay.