One of Cary Grant's favorite projects. He always maintained his role in this film was most like his real personality. He claimed he kept in touch with most of the girls as they grew up and had families of their own.
The scene in the dinghy where the small boat gets passed by two large ships was filmed on the Universal Studios back-lot in a large tank on a sound set. One of the child stars, Stephanie Berrington [now Stephanie Berrington McNutt] who played Elizabeth, in an interview said, "It was a large tank like a swimming pool. We had wave-making machines which were logs attached to steel arms that kept slapping the water to make waves. The larger ships were actually projected onto screens above the water. At first, the dinghy was just floating free and was not attached to anything. In one of the first few takes, it took on so much water that it sank (it wasn't supposed to) and most of the children were thrilled. It was like going for a swim. There was one child, however, who did not know how to swim so the directors and producers all jumped into the water in their good clothes and expensive watches to "save" us. Needless to say, most of us didn't want to be saved at all! Photos were taken and I believe they were published in the Los Angeles Times."
Cary Grant was offered the role of Henry Higgins in My Fair Lady (1964) but turned it down to star in this movie. He wanted his Charade (1963) co-star Audrey Hepburn to play Catherine, but she was already committed to My Fair Lady (1964).
The penultimate film of Cary Grant's career, it was the last time he played a romantic lead. In the following year he refused the romantic lead in his final film, Walk Don't Run (1966), a remake of The More the Merrier (1943) set during the 1964 Tokyo Olympics, because, at 61, he felt he was too old to be a believable love interest for the much younger lead female character.
The film features the same piece of stock footage of a submarine firing a torpedo that was used in Cary Grant's previous World War II comedy Operation Petticoat (1959).