The series was originally intended to air for only one season. Ball and Desi Arnaz's studio, Desilu, was losing money. Arnaz persuaded Ball to return to series television only to help their studio become viable again. Ball agreed to do the show only if it aired on Monday nights like I Love Lucy (1951) had and if her former co-star, Vivian Vance, and her former writers would be involved.
Vivian Vance refused to agree to appear on this show unless she was allowed to wear nice clothing. The days of a frumpy best friend were over. This was agreed to, and she signed the contract.
When Joan Crawford was asked during an interview how she liked working with Lucille Ball on the show, her response was, "And they call ME a bitch - Lucy can out-bitch me ANY day of the week!"
In the episode where Lucy and Viv are stuck in the shower and it starts flooding, Lucille Ball was actually drowning for a few seconds, she was stuck underwater and couldn't get herself up. When you see Viv hoisting her up, she is actually saving her life. They kept this take for the episode that aired.
William Frawley's last television appearance was on October 25, 1965, season four, episode six, "Lucy and the Countess Have a Horse Guest". He played a horse trainer at a barn Lucy and Ann Sothern are visiting. After they talk, she said, "You know, He reminds me of someone I used to know." This was Frawley's last film appearance. He passed away the following March.