Susan "SuSu" Applegate (Ginger Rogers) is a twenty-something who is disappointed with her job prospects in New York City and decides to return home to Iowa. Finding that the train fare is more than she can afford, she disguises herself as a twelve-year-old girl in order to buy a child's half-fare ticket.
While running away from suspicious conductors after she's caught smoking, Susan meets Major Philip Kirby (Ray Milland), who actually believes she's twelve, and offers her his spare berth for the night. But the train is stopped by a flooded bridge, and Kirby naturally can't leave an "underage" girl stranded all by herself, so he convinces her to stay at the nearby military academy where he works.
Said academy happens is run by Colonel Hill (Edward Fielding), whose daughter Pamela (Rita Johnson) just happens to be Kirby's fiancée. Pamela is actively thwarting Kirby's desire to return to active service, so that she can have a lovely wedding and long honeymoon, and the couple can remain stateside. Unfortunately, Kirby—who wants to take a more active role in the war—doesn't know anything about this deception.
At the academy, Susan finds an unexpected ally in Lucy (Diana Lynn), Pamela's teenaged younger sister, in whose room she is staying. Lucy—who is studying biology, and can tell that "SuSu" couldn't possibly be twelve (her calves have no baby fat and her smile lines are too deep)—promises to keep Susan's secret if she'll help her scuttle Pamela's plans.
How will Susan survive in this academy full of horny boys, especially with her own feelings for Major Kirby growing? Ah, let the screwball comedy answer it for you.
This film provides examples of:
- Contrived Coincidence: One of the academy's cadets turns out to be the son of Mr. Osborne (Robert Benchley), a Casanova Wannabe former client of Susan's in New York. Uh oh.
- Hollywood Kiss: The ever so famous Fade Out kiss.
- Devilish Hair Horns: Pamela wears victory rolls, reflecting her cold and mean-spirited personality.
- Hormone-Addled Teenager: "SuSu" gets dumped into a whole Military School full of younger-teenage boys who only get to see girls on special occasions. They spend a lot of time trying to get to first base with her, and even draw up a schedule of who gets to see her and when.
- Kiddie Kid: In film, Susan Applegate's attempt as a twelve-year-old comes off more as a six-year-old.
- Fiery Redhead: Susan says that she used to spit at people as a child.
- The Film of the Play: Billy Wilder and Charles Brackett loosely adapted their screenplay from the 1923 play Connie Goes Home by Edwin Childs Carpenter.
- Mistaken for Cheating: When the train is stopped, Pamela gets onboard looking for Kirby and finds Susan (looking her real age for the moment) in his compartment.
- Mistaken for Prostitute: Implied in the opening scene, when an elevator boy doesn't believe Susan when she says she's going up to a strange man's apartment to give him a scalp massage.
- Nursery Rhyme: SuSu sings "A-tisket, A-tasket" on the train in a vain attempt to exude innocence.
- Paper-Thin Disguise: Rogers looks less and less like a twelve-year-old and more and more like Ginger Rogers over the course of the movie.
- The Remake: Remade in 1955 as the Martin and Lewis vehicle You're Never Too Young, with Jerry Lewis in Rogers' role.
- Romantic False Lead / Disposable Fiancée: It's not like there's any chance Kirby is going to wind up with Pamela instead of Susan.
- Running Gag: All the cadets at the school seem to use the same pick-up line. Susan even uses it on Kirby in the last scene.
- Secret-Keeper: Lucy, who uses her knowledge of Susan's actual age to more or less blackmail her into helping sabotage Pamela's plans to keep Kirby out of active duty.
- When the train officials ask Susan to say something in Swedish, she says Greta Garbo's famous line from Grand Hotel.
- Another one to Veronica Lake, as all the girls from the girls' school copy her famous peek-a-boo hairdo.Cadet Clifford Osborne: Well, the bus is here. The zombies have arrived.Susan: Who?Cadet Clifford Osborne: [disdainfully] The girls from Miss Shackleford's school.Cadet Lt. Miller: We use 'em for women. May as well warn you, there's an epidemic at Miss Shackleford's school.Susan: An epidemic?Cadet Lt. Miller: Yeah, they all think they're Veronica Lake. Look. [cue to all the girls turning their heads, all with the exact same hairdo]
- Smoking Is Cool: At least in the film, it's the cool adults who do it.
- Snowball Lie: The whole story.
- Take That!: Early in the film, a girl mentions that she wants to buy a movie magazine where the lead story is "Why I Hate Women, by Charles Boyer." Wilder had clashed with Boyer the previous year when the actor refused to do a scene Wilder had co-written for Hold Back the Dawn.
- The Talk: Type 2. Major Kirby hilariously gives little "SuSu" an analogy of flies and a lightbulb. "SuSu" being the light of course. After the talk, she coyly answers:Susan: I'll try and be a better lightbulb, Uncle Philip.
- Telegraph Gag STOP: Pamela and the Colonel think that Kirby has slept with Susan (seeing her in a moment where she didn't look 12), so Kirby tells SuSu that he needs her to clear his name. The gag comes in when Kirby realizes he needs to tell SuSu's parents about taking her home with him.Major Kirby: Now, about your parents.Susan: Well, there's just my mother.Major Kirby: Well, I'll send her a telegram that will absolutely put her at ease.Susan: What kind?Major Kirby: Well, how 'bout, uh, "Met your daughter on train and looked out for her last night..."Susan: STOP!Major Kirby: "Stop. As we cannot proceed on account of high water, I'm taking her home with me."Susan: STOP!Major Kirby: "Stop. Don't worry. Signed Kirby". Will that fix it?Susan: That will certainly fix mother!
- That Came Out Wrong: Likely why Susan objects to the above telegraph gag.
- Unresolved Sexual Tension: Loads and loads. Mostly Susan towards Major Kirby, but you know, if it weren't for the age thing...
- Zany Scheme: Susan dressing up as 12-year-old just to get half fare.