In the 1979-1980 season, Mackenzie Phillips was dealing with drug addiction. When she entered rehab in 1980, her character, Julie, married Max and moved to Houston. In the seventh season (1981-1982), Phillips returned as a guest for a two-part episode in which Julie and Max deal with marital problems. In the ninth and final season (1983-1984), Phillips collapsed on-set. Producer Patricia Fass Palmer asked Phillips for a urine test. Phillips told Palmer not to bother. Phillips was quietly fired, and Julie was permanently written out of the show.
The premise for this show (a family led by a single working mom) was inspired by actress, writer, and single mom, Whitney Blake. One of Blake's children, Meredith Baxter, would go on to play a sitcom mom on Familienbande (1982).
The travel agency set where Barbara and Max work during the final season was later used as Al Bundy's shoe store on Married with Children (1988). In a few episodes of this show, a "New Market Mall" sign is visible through the windows.
Bonnie Franklin nearly quit after fifteen episodes, because she was not pleased with the show's direction. She agreed to stay after being allowed more creative input into the series.
In 2012 One Day at a Time Won one of the TV Land Awards: specifically the Innovator Award. Original cast members Bonnie Franklin; Mackenzie Phillips; Pat Harrington and Glenn Scarpelli were all on hand to accept the award. Where Bonnie Franklin and Pat Harrington thanked Norman Lear, the audience and the cast, Glenn Scarpelli thanked fellow cast member Mackenzie Phillips for being such a "fearless and honest role model for the world." This was right after Phillips' brutally honest 2009 autobiography "High on Arrival" had been published.