According to Debbie Reynolds, Shelley Winters' psychiatrist advised her not to portray a woman having a nervous breakdown because, at the time, she was having a real-life nervous breakdown. "She's the kind of actress who becomes the part she's playing..." said Reynolds, "so all through the film she drove all of us insane!"
Debbie Reynolds drove Shelley Winters to work each day. One morning on her way to pick up Shelley, Debbie noticed a woman standing on Santa Monica Boulevard in a nightgown trying to flag down a ride. When Reynolds stopped and asked why she wasn't waiting at home, Winters replied, "I thought I was late."
As part of the contract for her short-lived self-titled sitcom, Debbie Reynolds had a deal with NBC to produce a film, and she loved Henry Farrell's story outline, as well as the notion of taking a dramatic role in a horror movie. NBC put up $750,000 and Reynolds invested $800,000 of her own, producing the film uncredited.
Shelley Winters decided that after they came in from the rain, her Helen character should have a moment when she kissed Debbie Reynolds Adelle character on the lips. This unscripted moment was filmed but removed from the final print of the movie to avoid attaining an R-rating.
Director Curtis Harrington shot certain scenes with the intention of using dissolves as a transition between scenes. He reluctantly had to remove the dissolves when producer Martin Ransohoff matter-of-factly stated that he didn't like them.
The film began production under the title "The Best of Friends," but Otto Preminger protested to the Motion Picture Association because he had already registered the similar title Such Good Friends (1971). Producer George Edwards quickly responded by changing the title to a line from the script: "What's the Matter with Helen?."
In September 1972, Helene Winston and Samee Lee Jones reunited on a segment of Love, American Style (1969) titled "Love and the Amateur Night." Essentially reprising their roles as an overbearing stage mother and a precocious Shirley Temple wannabe (named Debbie after "Helen" star Debbie Reynolds), Winston and Jones interrupt the honeymoon of a TV personality and hold an impromptu audition, with Jones again performing "Animal Crackers in My Soup" as Winston accompanies her on piano.
The trivia items below may give away important plot points.
The night before Adelle's death scene was shot, Debbie Reynolds awoke from a nightmare in which she was stabbed. When she arrived on set, she checked the knife and discovered someone had replaced the rubber prop knife with a real blade.
The marketing team created what is arguably one of the worst ad campaigns in horror movie history with a spoiler campaign that tipped off movie-goers to the ending (posters and ads featured photos of the body of Debbie Reynolds' character, murdered and strung up on a ladder) that totally robbed the film of its shock climax.
Director Curtis Harrington shot and edited Adelle's death with the intention that the scene would be "as harrowing and brutal as the shower scene in Psycho." Against his wishes, the scene was severely truncated because the studio wanted the film to garner a GP-rating.
Right after Adelle reads Helen the letter that explains the man whom she just murdered was actually bringing her good news, Adelle strikes Helen with the crumpled letter, almost exactly mimicking the scene in Lolita (1962), in which after reading Humbert's diary, Charlotte Haze - Shelley Winters - strikes Humbert with his diary.