The Incredible Mr. Limpet

Live-action/animated 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.

The Incredible Mr. Limpet provides examples of:
"George: You can't see him. You wouldn't want to.
 * The Adjectival Superhero
 * All Animation Is Disney: This wasn't a Disney film, but Disney gives a nod to the film in The Little Mermaid (see The Cameo below).
 * 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: Mentioned but 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.
 * The Cameo: Although not a Disney character, Mr. Limpet can be seen in the background during the "Under The Sea" number in Disney's The Little Mermaid.
 * Limpet now also appears in the background in the new Disney's California Adventure "The Little Mermaid" ride.
 * 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).
 * Cute but Cacophonic: Limpet gets turned into an Ugly Cute cartoon fish who can produce a "whale buster" strong enough to fight enemy submarines.
 * Fainting: When George Stickel 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.
 * 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.
 * If Only You Knew: George Stickel 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.

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 a lake, gets hit by lightning, and turns into a fish. However, he did wish for it earlier, and it was accompanied by creepy singing angel voices...
 * Like a Fish 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.
 * 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.
 * 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.
 * Now Do It Again Backwards: The method Admiral Spewter suggests to turn Henry Limpet back into a human being.
 * 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 2 until victory.
 * Roger Rabbit Effect
 * Tickertape Parade: Limpet dreams of having one for his war hero services.
 * Ugly Guy Hot Wife: A staple of Don Knotts comedies and, as usual, a Huge Girl Tiny Guy scenario.