Mary Wickes, the woman who played Madame LeMond in The Ballet, was one of Lucille Ball's closest friends, and also one of the very few people who could really make her laugh (In the 1970s, Lucille wrote a list of the people who could make her laugh on her organizer and Mary Wickes made the list!).
Mary was considered the role of Ethel Mertz, but Mary knew Lucille's character and her working style too well to agree. She believed that if she accepted the role, it would ruin their friendship. She played Madame LeMond really well, didn't she!
Mary also accompanied Lucille on her final visit to Vivian Vance before her death in 1979. While Lucille and Viv chatted, Mary gave them some private time by sitting at a corner. When they drove home from Viv's place, they cried hysterically because it was obvious to them that they would never see Viv alive again. Viv lost her life to cancer thereatfer.