Emma Stone was initially cast as Billie Jean King, but scheduling issues forced her to pass on the role. Brie Larson was ultimately tapped to replace her. After a few months, Larson dropped out. After Stone's schedule was cleared, she was able to take back the role.
Whilst riding in the car, Billie Jean King and Marilyn Barnett listen to an Elton John song. John and King were friends by 1974, and they co-wrote his hit single 'Philadelphia Freedom' as a favor to her.
The film sugarcoats Billie Jean King's love affair with Marilyn Barnett. In 1981, Barnett sued King, invoking the palimony law, and nearly destroying King's career. It took years for King to rebuild what she'd lost.
Bobby Riggs's hustling and male chauvinism were known prior to his match with Billie Jean King, but became more infamous afterward. In 1973, he guest starred as himself on an episode of The Odd Couple: The Pig Who Came to Dinner (1973), in which he hustled Oscar Madison out of everything, including his apartment lease and Felix. Riggs also gambled with Felix, betting that he would become a member of the male chauvinist club, Riggs' Pigs, if Felix lost. Billie Jean King also appeared in the episode.