When Marla and Lucy share the back seat of a car, much of their dialogue is improvised.
This was Warren Beatty's first acting role in a feature film since Town & Country (2001) and his first time as director since Bulworth (1998).
Andrew Garfield was originally cast in a role but later dropped out. Justin Timberlake and Alden Ehrenreich were considered to replace him.
Warren Beatty first pitched a Howard Hughes biopic as early as 1973. He continually tried to get a film involving Hughes off the ground every year or two since then. It could be said that it is a film forty years in the making.