Leonardo DiCaprio has signed on to star in and produce an adaptation of The Crowded Room, where the actor will play the role he's been eyeing for nearly 20 years, Billy Milligan, the first person to successfully use multiple personality disorder as a defense in a court of law. New Regency will produce alongside Leonardo DiCaprio's company Appian Way, with screenwriters Jason Smilovic and Todd Katzberg coming aboard to write the screenplay adaptation.