The Copperfin submarine was an exact scale model of a real US Navy submarine. However, for reasons of military security, equipment and operating mechanisms were of varying kinds and varieties not found on US submarines so the enemy could not get an accurate picture of what the interior of a Navy submarine looked like.
The appendectomy operation conducted by the character Pills (William Prince) was inspired by an actual appendix operation performed aboard the submarine "Seadragon" in 1942. The real-life appendectomy was performed by 22-year-old pharmacist's mate Wheeler B. Lipes with the help of an assistant. The two were able to extract the appendix of Seaman Darrell Dean Rector under very trying conditions with limited resources and skills. They used kitchen utensils and equipment including a strainer and bent spoons as retractors; alcohol taken from torpedoes, and sterilized pajamas as surgical gowns. The sub's crew had believed that Lipes was the most qualified person to perform such a life-or-death operation, as he had apparently observed appendectomies before. Lipes was persuaded to do the operation by his fellow crewmen. The operation took place 120 feet below the surface of the South China Sea. Afterwards, Lipes' actions were criticized by US Navy doctors and the US Surgeon General even considered court-martialling him. Over 60 years later, in April 2005, Lipes finally received the US Navy Commendation Medal, two months before his death. According to the 19 April 2005 Los Angeles Times obituary of Lipes, this operation was the first ever performed in a submerged submarine.
The appendectomy done in this film actually happened. It was performed on the USS Silversides SS236. Pharmacist's mate Thomas Mooere removed George Platter's appendix 150 feet below the ocean's surface. Photographs of the surgery are on display where this submarine is docked, in Muskegon, Michigan, at the Great Lakes Naval Memorial and Museum.
Two members of the real-life US Navy submarine Wahoo were consultants and technical advisers on this film, according to a story in the "New York Herald Tribune". They were crew member Andy Lennox and Lt. Cmdr. Dudley Walker Morton. As a way of saying "thank you" the chili and canned pumpkin used by "Cookie" is labeled as being made by "Lennox".
This film represents one of four movies made by Hollywood during the 1940s which were about or related to the US military's Dolittle Raid on Tokyo, Japan during World War II. The four movies (the first three considered "fictionalized") are this one, The Purple Heart (1944); Bombardier (1943) and Thirty Seconds Over Tokyo (1944), the latter being the most accurate and least fictionalized of the four.
Tony Curtis, in an interview aired on TCM, recounted the day when he went into a theater and watched this film and saw Cary Grant peer through a periscope at Tokyo Bay. That moment "took his breath away" and inspired him to become an actor. Other reports state that Grant inspired Curtis to join the navy. Both Grant and Curtis would later star together in the World War II submarine comedy Operation Petticoat (1959).
A press release announced that the children of Cary Grant's character Capt. Cassidy were played by the children of director Delmer Daves. Debby Cassidy was played by Deborah Daves and Michael Cassidy was played by Michael Daves. Both children's character's first names were the same as their real first names and both performances were uncredited.
Posters incorrectly advertised the film as "Destination Tokio" despite Tokyo's proper spelling appearing in the film's on-screen title. Upon the film's release on DVD, a variation of the poster using the corrected spelling was used for the cover.
Here is another story of an appendicitis attack on a Submarine in WWII. Frank T. was on the Tambor as a gunner's mate and had an attack and the cook nursed him back to health which was the protocol (not doing an actual surgery). When was going to be assigned to the Barbel, the doctors choose to do the surgery instead. The Barbel never came back from patrol. His next and final assignment was the Hammerhead where he was on it for the commissioning. His first assignment was on the Gar.
Although the Copperfin is regarded as a Gato-class boat, based on studio footage, she would more correctly be a Salmon-class or Sargo-class boat. The only Gato-class sub in commission on December 7th, 1941, the USS Drum, was first deployed to Hawaii in April, 1942 and began her first patrol three days before the Doolittle Raid. The Salmon, Sargo, and Tambor fleet submarines were the only boats in commission in 1941 with the range to reach Japan. Additionally, when Copperfin attacks the Japanese carrier it fires 4 torpedoes each from its fore and aft tubes, which would be the configuration of a Sargo or Salmon-class sub. (The Tambor's had six forward tubes.) The torpedo controls on the Copperfin show lights for a four and four configuration.