The star was spotted Thursday on the Los Angeles set of the movie, which tells the story of the historic 1973 tennis match between King and Bobby Riggs (played by Steve Carell), sporting glasses and wearing a white tennis outfit with blue and yellow stripes.
Stone, 27, also traded her red hair for King’s brunette locks.
The legendary match between King – who at the time was the No. 1 player in the world – and Riggs – who had been retired for several years – is famed for helping spur a larger conversation about gender equality.
King ultimately defeated Riggs in a tennis match at the Houston Astrodome, and it became the most-watched television sports event of its time – and turned King into a sports superstar.