Was offered the role of Beth McCarthy in Cocoon (1985). Director Ron Howard wanted to reunite co-star Don Ameche with one of his former leading ladies and he thought of Joan. Unfortunately, she was in frail health at the time and supposedly turned down the role, a decision she later regretted when "Cocoon" became one of the biggest box office hits of 1985 and spawned a sequel. The part was played by Gwen Verdon. Miss Bennett did not, in fact, turn down the role. Rather, she was talked out of taking it by her fourth husband, David Wilde. Wilde insisted that the film too closely resembled the 1956 film Invasion of the Body Snatchers (1956). He also felt that it was beneath Miss Bennett's dignity to be working under "Opie Taylor" or "Richie Cunningham".
Was pregnant with daughter Melinda Markey while filming Little Women (1933).