Season 1 (1968–1969) Day portrays Doris Martin, a
widowed mother of young sons Billy and Toby (
Philip Brown and Todd Starke). As the series begins, she has brought her boys home to her father's rural ranch in
Mill Valley, north of
San Francisco, California, after living in New York City for most of her adult life. Other characters during this initial phase of the program include Doris's father Buck Webb (
Denver Pyle) and their naïve hired ranch hand, LeRoy B. Simpson (
James Hampton). Their housekeeper initially is Aggie Thompson (
Fran Ryan, who left after the first 10 episodes to replace
Barbara Pepper as Doris Ziffel in
Green Acres). The character left without explanation and was replaced by Juanita (
Naomi Stevens).
Lord Nelson is also included in the opening credits cast as Lord Nelson, the family's
sheepdog.
Season 2 (1969–1970) Doris begins to commute from the ranch to San Francisco, where she starts working as an executive secretary at ''Today's World
magazine. New workplace characters are added: McLean Stevenson (who would later leave the series to star in M*A*S*H) plays her boss, Today's World'' editor Michael Nicholson, who is often referred to as 'Nick' by the other magazine executives;
Rose Marie plays Doris' friend Myrna Gibbons, a fellow secretary at the magazine;
Paul Smith portrays Ron Harvey, the magazine's assistant-editor and Myrna's boss. Pyle, Brown, and Starke remain regular cast members, while Hampton appears in only one episode, his character now married and owning a gas station in Mill Valley. Lord Nelson still appears uncredited as the family sheepdog in most episodes this season. The ranch no longer has a housekeeper, and no ranch hand was hired to replace LeRoy.
Season 3 (1970–1971) Doris tires of the commute between her work and the ranch and relocates herself, the boys, and the dog to San Francisco, where they rent an apartment above an Italian restaurant owned and operated by married couple Louie and Angie Pallucci (
Bernie Kopell and
Kaye Ballard). At first Louie is angry with Angie for renting the apartment to a widow with children and a large pet, but he eventually cherishes their new tenants after Billy and Toby praise his pizza. Angie also becomes one of Doris' best friends. Doris begins writing articles for the magazine under the auspices of Mr. Harvey, the assistant editor, but is still mainly a secretary. All of the regular characters from the previous season remain, with the exception of Pyle's Buck, who appears in only two episodes; no episodes from Season 3 onward take place on his ranch. (Pyle, however, remains on the show's staff behind the scenes, serving as a frequent episode director.) Hampton's character LeRoy appears in only one episode; he now lives in Montana and travels the rodeo circuit to raise the money to buy his own ranch. In this season Doris' nemesis, Willard Jarvis (
Billy De Wolfe), moves in next door, causing trouble for her and her family in a few episodes. Lord Nelson again is not included in the opening credits cast list, but appears uncredited in a handful of episodes this season.
Seasons 4–5 (1971–1973) The fourth season sees a radical change in the series. Day's character suddenly becomes a swinging single career woman who goes by Miss instead of Mrs. The entire cast from previous seasons, other than Day herself and occasionally the Palluccis and Jarvis, is gone; even Doris Martin's two sons are no longer in the cast with no explanation given, and are never referred to again. Doris Martin, still working for ''Today's World'', now has a new editor, Cy Bennett, played by
John Dehner, and she is now a full-time staff writer, and later an associate editor.
Jackie Joseph joins the cast as Doris' friend and Cy's secretary at the magazine, Jackie Parker. Doris lives in the same apartment and the Palluccis, Angie in particular, are still on hand in the fourth season. In season 5, there is no mention of the Palluccis owning the building; the estate of the owner, an elderly man named Mr. Carter, sells the building after Carter's death to Doris' sometimes-nemesis, Mr. Jarvis, which initially alarms Doris, but she and the other tenants eventually accept him. In Season 4, Doris begins a romance with Dr. Peter Lawrence (
Peter Lawford), which lasts until late into Season 5. That relationship is followed by one with old boyfriend Jonathan Rusk (
Patrick O'Neal). The series continued with this format until Doris Day left the show choosing not to renew her five-year contract in 1973. Day placed a one-paragraph statement in
Variety saying more or less, "Television is not the be all end all". ==Change in premise==