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.
Warren Beatty turned down an offer of $1 million to play Howard Hughes in the TV miniseries "The Amazing Howard Hughes" thus enabling Tommy Lee Jones to star as Howard Hughes. That was one of Tommy Lee Jones' early break out parts.