Clark Gable became addicted to Italian food while making the film, and his weight ballooned to 230 lbs.
A much younger and slimmer double stood in for Clark Gable in the brief nude scene, which was only seen in silhouette.
Although Clark Gable and Sophia Loren did not get along during filming, he did help smuggle Carlo Ponti onto the island to celebrate her 25th birthday.
At one point Sophia Loren accused director Melville Shavelson of filming her from her less attractive side in order to favor co-star Clark Gable. She added, "He doesn't have to worry about his career any more, but I have to worry about mine." Gable immediately exploded, "What the hell is she talking about? Both sides of my face are lousy and my backside isn't much better." Relations between the two stars did not improve after that.
Just before the courtroom scene, Lucia dramatically and tearfully denounces Mike's and his lawyer's attempts to trick her and steal the boy, to which Gable's character remarks sarcastically, "I forgot, who won the Academy Award this year?" In fact, Sophia would become the first foreign actress to win an Oscar (Best Actress) for a foreign-language film, Two Women (1960, It.) the following year.
The film was shot in and around Naples and Sophia Loren had to sneak into the country to make the movie, because the Italian government was investigating her Mexican "marriage" to Carlo Ponti, who was still legally married to another woman.
This was the last movie Clark Gable made that was released during his lifetime. The 33-year age difference between him and Sophia Loren was blamed for the film's poor performance. There was in fact some surprise that he had accepted the part, since at a press conference while filming But Not for Me he had announced that he was no longer going to play romantic leads.