A live-action/animated World War II comedy from 1964, about a nebbish bookkeeper named Henry Limpet (Don Knotts) who dreams of being a fish... until one day he falls into the ocean and becomes one - a talking fish resembling a tilefish - and helps the U.S. Navy locate and destroy Nazi submarines.
- Always a Bigger Fish: Limpet is startled at the sight of a few small fish getting eaten by a big fish, which then got eaten by a bigger fish, which got eaten by an even bigger fish.
- Animal Talk: Once he's become a fish, Henry can speak to the ocean wildlife he encounters, and he can continue to speak English to boot.
- Animorphism: The whole plot, and while Henry didn't expect to actually turn into a fish, he's thrilled that he did.
- Attractive Bent Species: When the main live-action character turns into a cartoon fish, he ends up falling for another cartoon fish.
- Be Careful What You Wish For: Subverted. When Mr. Limpet makes his wish, an angelic chorus actually sings "Be careful" a few times before he goes through with it, but it turns out he really is happier as a fish. Though briefly he felt awful for leaving his wife and friend, who believed he drowned.
- Big Applesauce: Flatbush and Coney Island come into play here.
- Blind Without 'Em: Even underwater, Henry needs his glasses. This becomes a plot point when he loses them just as he's about to lead a big attack on the Nazis.
- By the Lights of Their Eyes: After Limpet goes into a cave, his eyes can be seen in the dark. The hermit crab Crusty is introduced when his eyes appear.
- The Cameo:
- Although not a Disney character, Mr. Limpet can be seen in the background at the end of the "Under the Sea" number in Disney's The Little Mermaid (1989).
- Limpet now also appears in the background in the Disney California Adventure and Magic Kingdom "The Little Mermaid" ride.
- He also appears in an episode of The Sylvester and Tweety Mysteries. Sadly, as part of a seafood buffet.
- Cartoony Eyes: He even wears pince-nez glasses (although they're not pince-nez when he's human; this is especially obvious near the end of the film when Mrs. Limpet is giving him a new pair).
- The Commissioner Gordon: George Stickel acts as the go-between for Henry and the United States Navy, arranging for Henry's top secret work and its compensation to be paid to Bessie under his name.
- Cute, but Cacophonic: Limpet gets turned into a cartoon fish who can produce a "whale buster" strong enough to fight enemy submarines.
- A Dog Named "Dog": Ladyfish. Limpet is the one who names her and she's new to the whole concept of names, so the blame rests squarely with him. Also, he nicknames the hermit crab "Crusty" as a shortening of "crustacean".
- Earned Stripes: At the beginning of the movie Henry Limpet's best friend, George Stickle, has just been promoted to Machinist's Mate Second Class in the U.S. Navy, and shows off the stripes on his uniform sleeve to Henry. He receives a promotion to Chief Petty Officer during the course of the film and does it again.
- Faint in Shock: When George Stickle hears the supposedly drowned Henry Limpet's voice coming from the sea, he faints dead away —probably because he thinks he's hearing Henry's ghost.
- Flashback Effects: The movie starts in the present day Pentagon, with two U.S. Navy officers preparing for an upcoming assignment. As one of them remembers past events that apply to the current situation, the screen has a wavering Dissolve and starts to show those events.
- The '40s: The main action of the film is set in the years 1941-1945.
- Gratuitous German: The German in the film starts out sounding legit but quickly descends into this.
- Handy Helper: Limpet loses his glasses, so his crab friend Crusty becomes his eyes.
- Heroic Dolphin: Limpet turns into an animated one, saving the day.
- If Only You Knew: George Stickle is trying to explain to Bessie that her husband, Henry, is still alive, but can't tell her the truth: that Henry has turned into a fish.George: You can't see him. You wouldn't want to.
Bessie: I do want to. How can you say a thing like that? Why can't I see him?
George: It's impossible. His work for the Navy is top-secret. Just be happy with his paycheck. Don't even mention his name to anyone.
Bessie: There's something fishy about this.
George: You said it!
- Lightning Can Do Anything: Limpet falls into the Atlantic Ocean at Coney Island, is affected by a powerful electric effect that causes X-Ray Sparks, and turns into a fish. However, he did wish for it earlier, and it was accompanied by creepy singing angel voices basically singing, "Be careful..."
- Like a Duck Takes to Water: Limpet is fascinated by fish, and at one point says, "I wish, I wish I was a fish." He gets his wish, and acclimates very quickly.
- Little "No": George says "No" softly when he finds out that Limpet has been turned into a fish.
- Love Triangle: Two mild examples.
- Henry, Bessie, and George hang out together all the time. George is Henry's platonic best friend. Bessie is married to Henry, but several times it is at least implied that Bessie had more fun with George than with Henry (not *that* kind of fun). At the end of the flashback, Henry asks George to take care of Bessie. At the end of the movie, George mentions that he and Bessie have been happy together for a long time, indicating that they got married after Henry's incident.
- After Henry's transformation, he falls for Ladyfish, but is still married to Bessie. By the end, he and Bessie both realize it is for the best if they just let go. Henry swims off with Ladyfish, and George and Bessie get married.
- Make Me Wanna Shout: Limpet gained a vocal weapon when he was turned into a fish. Though it's less a sonic shriek and more a sonic boom, as he generates a thundering percussive shockwave. It's put to good use at the climax of the movie when he uses it to guide "thrum" seeking German torpedoes to destroy the Nazi U-boats that launched them.
- Match Cut: Limpet's fantasy of being a hero ends with a shot of a bomber, which then dissolves into a manta ray that knocks Limpet's eyeglasses off.
- MayDecember Romance: Ladyfish implies that she only came of "spawning" age very recently. Very recently, as in the moment she met Limpet.
- Misguided Missile: A wolf pack of Nazi submarines has fired torpedoes at an Allied convoy. The title character discovers that the torpedoes have been modified to follow his "thrum" (the booming call he can make). He uses this to make the torpedoes follow him away from the ships and hit the U-boats that fired them.
- The Musical: There are several songs interspersed through the movie, but all are presented as fantasy sequences. Don Knotts's singing is...underwhelming.
- No Need for Names: All of the sea creatures seem unaccustomed to the concept of names. Limpet names a hermit crab "Crusty" and a female fish "Ladyfish".
- No Social Skills: Limpet isn't exactly the most socially well-adjusted human.
- Now Do It Again, Backwards: The method Admiral Spewter suggests to turn Henry Limpet back into a human being.
- Reality Has No Subtitles: When German sailors are talking to each other aboard U-boats and in a conference room, they speak untranslated German. When the German scientists and naval officers are talking to each other while researching "Das Limpet", they start out speaking untranslated German. Later on they start mixing German and English together in a somewhat understandable manner.
- Rushmore Refacement: While caught up in an imagined celebration of his success, Limpet imagines Mount Rushmore with his (fish) head added to it.
- Spinning Paper: After Henry Limpet destroys the attacking U-boat wolf pack, a series of spinning newspaper headlines list the final events of World War II until victory.
- Tickertape Parade: While he's protecting the convoy heading to Europe, the title character Limpet daydreams about the awards he will receive for his war hero services, including such a parade in his honor.
- Too Dumb to Live: The Nazi response to Limpet's "thrum", which they only know is an American system that picks out their subs to call in naval fire, is to equip their torpedoes with systems to track it. There is literally no scenario where this doesn't result in them targeting their own ships. It's partially justified since they have no idea Limpet is a sapient fish.
- Ugly Guy, Hot Wife: A staple of Don Knotts comedies and, as usual, a Tiny Guy, Huge Girl scenario.
- Whole Episode Flashback: The entire movie is told by an older George to his superior when Limpet is discovered to still be alive and has been teaching dolphins.
- Wronski Feint: Henry luring the Nazi "thrum-seeking" torpedoes into hitting the U-boats that fired them.
- X-Ray Sparks: When Henry turns into a fish, his skeleton shows through his body.