The famous scene, in which Brando's character uses a stick of butter during a sexual assault, was not originally in the script. The two men told Schneider about that scene right before the filming.
"The sequence of the butter is an idea that I had with Marlon in the morning before shooting," Bertolucci said in an event at La Cinémathèque Française, where he was speaking about Schneider, who had died two years before after a long struggle against cancer.
According to Bertolucci, he decided to conspire with Brando, because he wanted Schneider to depict true, authentic emotions, to react "as a girl, not as an actress."
"I wanted her to act humiliated. I think she hated me and also Marlon because we didn't tell her," Bertolucci said.
"I didn't want Maria to act her humiliation, her rage, I wanted Maria to feel… the rage and humiliation. Then she hated me for all of her life."
"I should have called my agent or had my lawyer come to the set because you can't force someone to do something that isn't in the script, but at the time, I didn't know that. Marlon said to me, 'Maria, don't worry, it's just a movie,' but during the scene, even though what Marlon was doing wasn't real, I was crying real tears. I felt humiliated and to be honest, I felt a little raped, both by Marlon and by Bertolucci," she said in a 2007 interview.
"After the scene, Marlon didn't console me or [apologize]. Thankfully, there was just one take."
Schneider's drug use led to her being fired from several movies. Despite that, she worked in more than 50 films and television productions between 1969 and 2008. Schneider died of cancer in 2011.
Remembering her, Bertolucci said, "Her death came too soon, before I could hold her again tenderly, and tell her that I felt connected to her as on the first day, and for once, to ask her to forgive me."