The original Broadway production of "Child's Play" by Robert Marasco opened at the Royale Theater in New York on February 17, 1970, ran for 342 performances and was nominated for the 1970 Tony Award for the Best Play. Robbie Reed was in both the original stage version and in this filmed production, but portrayed a different character in the film.
Marasco based the play on his experiences as a Latin, Greek, and English teacher at his alma mater, Jesuit-run Regis High School in Manhattan, where a teacher did commit suicide by jumping out of a window after giving his students an assignment.
Pat Hingle, Fritz Weaver and Ken Howard played the Preston, Mason, and Bridges roles on Broadway. Both Weaver and Howard won Tonysfor their work. David Rounds recreated his role from the Broadway production. The play ran 342 performances.
Marlon Brando originally signed for the role of Joseph Dobbs (Robert Preston), but quit the production before principal photography commenced. According to Bob Thomas's "Brando: Portrait of the Artist as a Rebel", Brando quit the production when he realized that James Mason had the better role, and that his flagging career would soon be revitalized by the The Godfather (1972). Preston, a fine actor, received poor reviews for his performance from Pauline Kael, among others. Brando subsequently was sued by producer David Merrick.
Marlon Brando had, in fact, already made The Godfather (1972) by the time he came to start work on this film. It has been alleged - notably by Pauline Kael - that tyro producer David Merrick fired Brando as an elaborate publicity stunt, both for the film and for himself.