Making this movie was the first time Ingrid Bergman had been on a Hollywood sound stage since the 1940s--all her subsequent films up to that point had been made in Europe, even those for American studios.
The play had been a comeback vehicle for Lauren Bacall following several years of inactivity once screen roles dried up. "Cactus Flower" was an enormous hit on Broadway, and Bacall garnered strong personal notices for her performance as Stephanie, playing the role for nearly two years. She was understandably disappointed when producer M.J. Frankovich cast Ingrid Bergman in the film version.
The three kids seen behind the GTO in the GM 5th Avenue showroom during Walter Matthau and Goldie Hawn's NY walkabout are David Matthau and Jenny Matthau and I.A.L. Diamond's son Paul Diamond
Tuesday Weld turned down the role of Toni Simmons, which earned Goldie Hawn an Oscar for Best Supporting Actress.
In the record store, a customer approaches Toni and asks her a question. The album he is holding happens to be the original cast recording of the musical "Mame" starring Angela Lansbury. This is an homage to the film's director Gene Saks, since he also directed "Mame" when it opened on Broadway in 1966.