Here's an episode of the MARY series that David Isaacs and I created for Mary Tyler Moore in 1985. Thanks to reader Benson for posting it on YouTube. This is the episode that features Katey Sagal singing. We knew she was a terrific singer (she was one of Bette Midler's Harlettes) but the character she played in the show was a real curmudgeon, not the kind of person who would just break into song.
So we constructed a story to justify it. The episode was directed by Ellen Falcon, written by me and David, and Richard Gilliland was the guest-star.