Ida Lupino was initially cast in The Milky Way (1936) until illness forced Dorothy to replace her.
Retired at the time, Dorothy was asked to test for the role of "Melanie" in Gone with the Wind (1939). She did, claiming it was the only role that could have persuaded her to return to the screen.
Supposedly, the one-time secretary to RKO had a clause in her contract that agreed that if her option was ever dropped, she had the option of returning to her job in the studio's secretarial pool.