Based on the 1981 novel The Minds of Billy Milligan and set in the '70s, The Crowded Room is based on the true story of a man with Multiple Personality Disorder (now officially called Dissociative Identity Disorder) - 24 personalities to be exact - who was arrested and charged with armed robbery and the sexual assaults of three women at Ohio University. He claimed the assaults were committed by two of his personalities without his knowledge, one of which was Adalana, a lesbian who had been deprived of affection and committed the assaults with Milligan's body.
According to author Daniel Keyes' website, the other personalities include Ragen, a Yugoslavian communist who is full of rage and extremely strong; Allen, a conman; Philip, a criminal who commits petty theft; David, an 8-year-old; Tommy, an escape artist; April, who only wants to kill Milligan's abusive stepfather; Kevin, a drug dealer who was behind one of the robberies Milligan committed; Arthur, an Englishman; the Teacher, who is only one that can put all of the personalities together; and many others, including more children (both male and female) and men and women as well.
The case became so famous because Milligan was the first person to successfully plea not guilty by reason of insanity. It's also considered to be one of the most shocking and disturbing cases of MPD recorded in history.
Cases like this are always preceded by some form of childhood trauma. Milligan reportedly suffered abuse as a child by the hands of his stepfather - both physical and sexual abuse. Often when suffering abuse like that, children may begin to form different personalities in order to escape it, so to speak.
James Cameron (Titanic, Avatar) began trying to get this film made decades ago with Twentieth Century Fox, with John Cusack set to star as Milligan. But the project went on hiatus over 10 years ago. The film was set to go into pre-production and the script was finished, but Sandy Acara (who had joint control of the project) filed a lawsuit against Cameron, stating that she deserved six times what she was set to be paid (1.5 million instead of 250k). Milligan even filed a lawsuit himself, saying he wanted 9 million for having to relocate himself to Los Angeles for the film.
As a result, the film halted and never got picked back up again, until now. Hopefully it'll go more smoothly this time around. This time, New Regency will be making the film with Leo. Jason Smilovic (Lucky Number Slevin) and Todd Katzberg are set to be the screenwriters, with DiCaprio set to co-produce with Alexandra Milkman and Jennifer Davisson.