The shot of the station wagon during the show's opening credits is from Alice Doesn't Live Here Anymore (1974).
Diane Ladd, who played Flo in Alice Doesn't Live Here Anymore (1974), joined the cast in the fourth season as Belle Dupree. The new character served as a replacement for Flo (Polly Holliday), who left for her own series, Flo (1980).
Henry's (Marvin Kaplan's) wife Chloe was talked about for years before she was finally seen. In her only appearance, she was played by Ruth Buzzi.
When Diane Ladd left the series, her absence was explained by having Belle finally sell one of her songs and moving away to become a professional songwriter.
The actual restaurant building on which this show is based is located at 1747 NW Grand Avenue, Phoenix, Arizona. It is currently called Pat's Family Restaurant. It was known as "Mel's Diner" from 1976 to 1985. Google Earth's ground view still shows the name as "Mel's Diner."