Before filming began, Orson Welles warned director Richard Fleischer that he would be far more difficult to direct in this film than he had been a year previously, when he appeared in Fleischer's "Compulsion". Although Welles had two roles in this film, he found neither one interesting, disliked his leading lady Juliette Greco and was all too aware of the inadequacies of the screenplay (written under a pseudonym by his old friend Darryl F. Zanuck, the producer). By his own account, Welles cut a number of his own speeches and generally made his role smaller, so that he would not become too bored. Director Fleischer later claimed that he had been quite willing, however, to do his own stunts in the film, as that would be a way of alleviating his boredom.
Richard Fleischer had also directed Orson Welles and Bradford Dillman in " Compulsion" the previous year.
Richard Fleischer writes in his autobiography that he accepted the script of "Crack in the Mirror" only because the producer Darryl F. Zanuck asked him for Juliette Greco with whom Zanuck was deeply, madly in love with. Fleischer did not want to take the risk of telling Zanuck that the script was lousy in front of Greco as didn't want Zanuck to lose face in front his girlfriend.
Darryl F. Zanuck was so mad about Juliette Greco that he would intrude during the rehearsal of a scene. He did not care about the director saying "Cut" before which no one on the set was allowed to do. Richard Fleischer tells in his autobiography that the mogul seemed to ignore this worldwide rule and behaved like a spoiled child because of Juliette Greco's presence.
Sally Kirkland's debut.