Valerie Harper appeared in (and darn near stole) the first episode of The Mary Tyler Moore Show in 1970 and many thereafter. Her Jewish, agonizingly-single character of Rhoda Morganstern provided a nice contrast to Mary’s white bread niceness. And after veteran character actress Nancy Walker began appearing occasionally to play Rhoda’s mother, you had another sitcom just waiting to happen. Finally, in 1974, it spun off on its own, largely under the creative direction of writer-producers Lorenzo Music and David Davis.

Harper and Walker were at the center of it all, joined by Julie Kavner as Rhoda’s younger sister, Harold Gould as her father, and a number of characters who were probably intended as regulars but didn’t stick around long. This included David Groh, who played a man who wooed and eventually wed the title character. Though the wedding episode drew monster ratings, the show lost a great deal of its edge with a married Rhoda. Eventually, they separated and the show never quite regained its pre-marital momentum. In all, it lasted five seasons.

The most interesting character on the show, and maybe the most popular, was never seen. It was Carlton, the perpetually-inebriated doorman of the building in which Rhoda lived — a man heard primarily over that building’s intercom. He did make a few on-camera appearances but something always got in the way, preventing the audience (and even Rhoda) from seeing his face. Carlton was so popular that when Rhoda got married, the producers made sure the newlyweds made their new home in the same apartment house. (One of those producers, Mr. Music, provided the voice of Carlton. In 1980, Carlton was finally seen — in the pilot for what was intended as a weekly, prime-time animated program, Carlton, Your Doorman. The one episode produced won an Emmy as that year’s Best Animated Special but failed to become a series.)