Here’s the time when Mary Tyler Moore popped in to the Late Night studio, having been across the hall doing another show, and sat down with Letterman for a few minutes.
The show they talk about doing together was The Mary Tyler Moore Hour, which was a variety show cum sitcom, and also featured Michael Keaton. This is a clip from the episode that guest starred Gene Kelly.
You can find full episodes on YouTube, and see Dave on their with Mary.
A few years later, Mary dropped by the Late Show, to plug her new show New York News, and ended up amusing Dave with her language.
New York News was an hour long drama, that ran for half a season, and featured one of the most 90s title sequences you could encounter.