The part of Carol was originally intended for Marilyn Monroe but the project was shelved after her death.
Stella Stevens' co-starring role in this film opposite Dean Martin led to a falling out with her The Nutty Professor (1963) co-star/director/paramour Jerry Lewis, who refused to speak to her for two decades. Martin and Lewis were famously feuding after the breakup of their comedy duo from the 1950s, themselves not speaking for years. Only her unannounced backstage visit after seeing Lewis perform in "Damn Yankees" on Broadway in 1995 brought the two together again.
Shelley Morrison, who plays Stella Stevens' friend and co-worker in the opening scene in the department store, later gained fame as Sister Sixto in the 1960s TV show The Flying Nun (1967), and more famously as Rosario in Will & Grace (1998).
This was the last mainstream Hollywood movie to be photographed by the legendary cinematographer Lee Garmes, who described it as "a comedy treated as a drama in the lighting" - something most reviewers missed.
A joke early in the movie is that Muriel Laszlo watches old movies at night, in which all the actors are dead. The first time Muriel and Carol are together unpacking Carol's things, Muriel says she had been watching an old Kay Francis and George Brent film. Ironically, both actors were probably alive during the production of this film. Kay Francis died in 1968, the year this film was released, but George lived until 1978. Sadly, in the era "Save A Marriage" was made, old movies and their stars were not held in high esteem, and George and Kay, long forgotten, may have simply been assumed to be dead.