When Olivia de Havilland agreed to make this movie, director Robert Aldrich called Bette Davis to give her the good news. He also requested she keep the news a secret until he returned in two days, when he would legally inform Joan Crawford and her lawyer by letter. However, Davis didn't listen - she called her press agent, Rupert Allan, who immediately leaked the story to the press.
Director Robert Aldrich had to take three planes, a train, and a taxi up a goat trail to get to Olivia de Havilland's house, which was in the mountains of Switzerland. It took him four days to convince her to step in and replace Joan Crawford.
Because there was no time to redo the costumes for Miriam, many of her clothes came from Olivia de Havilland's personal wardrobe. Of note is the dress (green silk chiffon) that de Havilland wears for the dinner scene with Davis and Cotten, which was from Christian Dior (by Marc Bohan) Spring/Summer 1964. The dress (including matching shoes) was sold by de Havilland's family in September 2019 (55 years since de Havilland joined the film) for $8,125.
Second movie in a row in which Olivia de Havilland stepped into a role originally announced for Joan Crawford. The other being Un giorno di terrore (1964).
The casting of Olivia de Havilland to replace Joan Crawford, and the reshoots that required, inflated this film's budget to over $2.235 million, about twice what had been spent to produce Che fine ha fatto Baby Jane? (1962). This film was originally budgeted at $1.5 million.