Five years had passed since I Love Lucy had ended its run. After 13 one hour specials, under the title The Lucy-Desi Comedy Hour, across 3 seasons (1957-60), Lucille Ball & Desi Arnaz had divorced. Arnaz, now President of their joint production company, Desilu, asked his ex-wife to return to headline a new series, seeing as how Desilu was down to one series on the schedule (The Untouchables). Lucy agreed.
The Lucy Show, like I Love Lucy before it, aired on Mondays on CBS, and spent six seasons, netting Lucy 2 Emmy Awards, to go with the 2 she won for I Love Lucy. The staff of writers, including Bob Carroll, Jr. & Madelyn Davis, were brought back, but things had changed. Trying to rewrite some classic I Love Lucy episodes as solo vehicles for Lucy didn't work out so well this time. Over the course of six seasons (1962-8), Lucy Carmichael went from being a widow to simply a single woman, and the locale changed from Connecticut to California halfway through the series.
In addition to the writing staff, musical director Wilbur Hatch and actress Vivian Vance returned, but neither were around at the end. Vance opted out after three seasons, choosing to remain in Connecticut and avoid the wear & tear of constant cross-country commuting. There were other cast changes. Charles Lane was cast as the manager of Lucy's bank early on, but left after being unable to recite his lines in front of a live audience. Lane at one point was pulling double duty, as he also had a recurring role on Petticoat Junction. Gale Gordon (ex-Our Miss Brooks, Dennis The Menace) was cast as Theodore Mooney, who took over at the bank in season 3, and moved with Lucy to California in season 4. By the time the series ended, Lucy was working for Mooney. Go figure.
After Vance left, it took some time before Lucy found her new sidekick in Mary Jane Croft, the wife of one-time producer Elliott Lewis, who would go on to work with Desi on The Mothers-in-Law. It just wasn't the same.
From the first season, here's "Lucy's Sister Pays a Visit". Said sibling is played by cartoon icon Janet Waldo. Also guest-starring a pre-Hollywood Squares Peter Marshall: