The 60-year-old actor will also be going bald for the film, which tells the true story of Eugene Allen, a White House employee who served eight First Families over the course of three decades, The Hollywood Reporter said.
"The Butler" is scheduled to begin shooting later this month in New Orleans. The film also stars Forest Whitaker, Oprah Winfrey, Vanessa Redgrave, Terrence Howard, John Cusack, Alan Rickman, Jane Fonda and Colman Domingo.
Besides "The Butler", Williams will also star in Phil Alden Robinson's "The Angriest Man in Brooklyn".
In the film, Williams will star opposite Mila Kunis, Peter Dinklage, Melissa Leo and James Earl Jones.
The film is the story of a stand-in doctor, who mistakenly tells an obnoxious patient he has 90 minutes to live.
