Something Only They Would Say / Live-Action Films

• 18 Again! (1988): When Jack decides to let his friend Charlie in on the fact that he's in his grandson's body, he tells him a few stories from their personal lives. Charlie first thinks that Jack just told David at one point, but he eventually comes around.
• In An American Christmas Carol the ghost of Jack Latham convinces Slade he's the real deal by telling him information only he'd know.
• The protagonist in The Assignment (1997), a Carlos the Jackal lookalike undercover as the real deal, proves his identity to his handler when his handler says "awfully warm for this time of year", to which he replies "but not as sticky as two summers ago". These are the two halves of a code phrase that was part of an assignment from long ago that his handler mentioned in conversation.
• The Batman films use this trope often:
  • In Batman Begins, after being asked who he was under the mask, Batman subtly reveals his secret identity to Rachel Dawes by mirroring a statement that she made to Bruce Wayne earlier in the film, when she caught him in public playing up his Upper-Class Twit persona and he tried telling her that that wasn't the real him.
    Bruce/Batman: It's not who I am underneath, but what I do that defines me.
    • In The Dark Knight Rises, Bruce also reveals his identity to Gordon with a Call-Back to Gordon attempting to comfort him after his parents died.
  • In Batman Returns, Bruce Wayne and Selina Kyle accidentally expose their identities as Batman and Catwoman to each other by unthinkingly reenacting a snippet of banter from their previous fight. In a slight variation, they switched lines in and out of costume.
    Batman/Selina: Mistletoe can be deadly if you eat it.
    Catwoman/Bruce: But a kiss can be even deadlier... if you mean it.
  • And this trope is also used in Batman (1989) and is how Bruce realizes the Joker is the thug who killed his parents. He repeats the phrase to Joker at the beginning of their final confrontation just before decking him.
    Jack Napier/Joker: You ever dance with the devil in the pale moonlight?
  • A villainous example happens in Batman & Robin. While Poison Ivy is seducing Robin she claims she can see him having his own "Robin Signal" in the sky. Later, she steals the Bat Signal and replaces it with Robin's symbol, and Robin, remembering the conversation, instantly realizes it is Ivy calling him, believing the signal to be a sign of her love to him.
• The Blues Brothers: Matt "Guitar" Murphy knows that the only two white guys who will walk into a soul food restaurant "dressed like Hasidic diamond merchants" and order dry white toast, four whole fried chickens and a Coke are Joliet Jake and Elwood Blues.
• Cinderella (1965) has Prince Christopher seem to recognize Cinderella, whether she's wearing rags or a ballgown, when she returns his thank-you's with, "You are most kindly welcome."
• A version of this occurs in Disney's Condorman, although it's not so much about identity as intent. Natalia and Woody (the titular hero) are sharing a moment together when he says the line, "I'll bring the dip if you bring the Dostoyevsky." Later, when it appears that she has changed her mind about defecting, she says it back to him, which prompts him to realize that she wants to be rescued after all.
• In The Count Of Monte Cristo, Fernand Montego is confronted by the Count immediately after finding the king chess piece he gave sixteen years ago to Edmont Dantes, his former best friend whom he betrayed and sent to a hellish prison. He doesn't make the connection until the Count/Edmond reminds him of their old game.
  Fernand: Monte Cristo.
  Edmond: King's to you, Fernand.
  Fernand: (drops the chess piece in shock) Edmond?
• In The Crow (1994), Sarah only realizes that the corpse-painted stranger who saved her from being hit by a car is her deceased friend Eric when he quotes the Arc Words "It can't rain all the time."
• In Elf, Buddy attempts this with a fake Santa. It... doesn't work.
  Buddy: If you're Santa, then... what song did I sing for you on your birthday?
  Fake Santa: Uh, Happy Birthday, of course!
  Buddy: Darn!
• The movie Face/Off uses a physical gesture of affection in this way. Specifically John Travolta's "smell my hand" gesture.
• From Ghost (1990): the word "ditto", which Patrick Swayze's character would use to respond to "I love you", to the point where his widow refuses to believe it's him when he tells her those three words through a medium.
• Zartan from G.I. Joe: The Rise of Cobra is quite fond of whistling the tune to "Jolly Good Fellow". When the man we think is the President comes out of the bunker, he goes into his office, relaxes and begins whistling. No prizes for guessing the tune.
• In the film adaptation of Harry Potter and the Goblet of Fire, Barty Crouch Jr., who is disguised as Mad-Eye Moody, nearly blows his cover when he performs a familiar facial tic (specifically licking his lips) in front of his father. Technically he does blow his cover, it's just that the father doesn't live long enough to spread the news.
• The Hunger Games: Catching Fire: How Finnick Odair convinces Katniss he's on her side — he tells her "Remember who the real enemy is."
• The Incredible Mr. Limpet: When Henry reunites with George after being turned into a fish, he tries to connive George (who, until now, thought he'd drowned) it's really him by recalling the times they spent with Henry's wife Bessie back in Brooklyn. George starts to ease down and laugh at these memories before freezing in shock, realizing that only his friend would know all that.
• In Indiana Jones and the Kingdom of the Crystal Skull, a character (Mack) tries one of these (he tells Indy a betrayal is "just like Berlin", where they were double-agents), which fails. The guy was really a traitor anyway.
• Played with in Inglorious Basterds. Lt. Hicox's accent made the German's suspsicious, but the dead giveaway was when he signed the number 3 incorrectly.
• In The Italian Job (2003), the villain realizes that he's on a date with the daughter of a man he killed years ago when she uses her father's trademark phrase, "I trust everyone; I just don't trust the devil inside them."
• It's a Wonderful Knife (2023): Winnie proves she's related to Gale in the alternate timeline after recounting an embarrassing incident from Gale's past that only a close relative would know about.
• Jack Frost (1998): After dying in a car accident and being resurrected as a snowman, Jack eventually manages to convince Charlie that it's really him as a snowman by calling him "Charlie boy" (which is what Jack used to call him by). Gabby, however, doesn't believe Charlie when she tells her the snowman is her husband. That is until Jack calls her on the phone, nonchalantly asking her to come to the cabin in the mountains, and Gabby recognizes her husband's voice and obliges.
• In the James Bond movie The World Is Not Enough, oil heiress Elektra King and terrorist Renard give themselves away as conspirators by using an identical aphorism - 'There's no point in living if you can't feel alive'. A few minutes later, Renard jams his hand into Bond's injured shoulder—something else he could only have learned from Elektra, though when Bond confronts her about this, she points out that Bond has been wearing a sling and any number of Renard's spies could have told him about this.
• Possibly invoked in the trailer for The Jungle Book (2016), which is narrated by Scarlett Johansson. The viewer might not realize who she's playing at first because she's simply narrating generically and ominously...but even if you didn't see who was talking, you'd know who it was the minute she said her last line, and it makes The Reveal of her character's identity all the more shocking.
  Kaa: Trussssst... in me...
• Just Like Heaven: David visits Elizabeth's sister to try and persuade her not to turn off Elizabeth's life support. On the way there he asks Elizabeth's spirit, who only he can see, for "dirt" on Abby to convince her that he's really speaking to her sister. Elizabeth supplies a few childhood anecdotes but David stresses it needs to be something only a sister would know. Elizabeth provides the story of Abby kissing her ex-boyfriend on her wedding day. David uses the story when he speaks to Abby but all it does is freak her out and she chases him out of her house.
  • The same story is what eventually convinces David's best friend Jack that David is telling the truth about Elizabeth because Jack is that ex-boyfriend.
• L.A. Confidential: when he's become the victim of a Have You Told Anyone Else?, Jack Vincennes says "Rolio Tomassi" as his dying words. That was the name Edmund Exley had just entrusted him with in a private conversation, and is a name he made up for his father's unknown killer, 'the guy who gets away with it'. When Dudley Smith gets nervous about who this "Rolio Tomassi" might be and what he might know, he starts asking around about him... to Exley, who realizes immediately that Dudley should have no way of knowing that name and confusing it with a real person unless he had something to do with Jack's murder.
• Played with in The League of Extraordinary Gentlemen, after the Big Bad and his mole have just attempted to destroy the Nautilus with planted explosives. The good guys’ mole, who has stowed away on the escape vessel with the bad guys, manages to send a message to the rest of the League with the coordinates of the escape route. They immediately realize it's from him because of the way the message opens - he's the only one in the world who would address them collectively as "my freaky darlings."
• Marvel Cinematic Universe
  • Avengers: Age of Ultron: Ulysses Klaue realizes Ultron is one of Tony Stark's creations when Ultron, after transferring a ten figure sum of money to Klaue for his vibranium supply, says, "It's like I always say, 'Keep your friends rich, and your enemies rich, and wait to see which is which.'" something Tony used to say.
  • Captain Marvel (2019): Carol explains early on this is the easiest way to test if someone is being impersonated by a Skrull, as they only retain a stolen identity's most recent memories. Fury figures out Talos has impersonated his boss when he calls him "Nicholas", since he'd told Carol that nobody, not even his mother, calls him anything other than "Fury". This gets a call-back when a Kree soldier appears to be taking Fury, Maria and Skrull prisoners to be ejected out an airlock. Leaning in to Fury, the Kree says "Just go with it... like Havana." Fury realizes this is actually Talos using Fury's own Bluff the Imposter move from earlier to reveal himself.
  • Spider-Man: Far From Home: After getting a violent and heartbreaking heads-up as to exactly how detailed Mysterio's illusions can be, Peter calls in Happy Hogan for a ride and asks for "something only [he] would know" to confirm he's talking to who he wants to see. A confused Happy recalls when he chaperoned Peter in Germany for the Avengers' civil war and they stayed in a hotel together; Peter ordered a pay-per-view movie for which Happy got the bill, and although the name wasn't listed, Happy could tell from the price that it was an adult film, and Peter didn't know how he would know that. Peter, now convinced it's actually Happy, cuts him off before he can say anything more embarrassing.
  • In Spider-Man: No Way Home, When the Webb-Verse Spider-Man arrives at Ned’s house, MJ and Ned are baffled as he introduces himself as Peter Parker, but from another world. When MJ asks him to prove he is Peter Parker, he snarkily quips that he doesn’t carry an ID with him as it “kinda defeats the whole anonymous superhero thing”. Moments later, when the Raimi-Verse Peter Parker also arrives there, he shows off some Spider powers confirming he too is an alternate version of Peter Parker. When Ned asks why he didn’t just tell them he was a Spider-Man, he too snarkily quips that he generally doesn’t go around advertising that, because it “kinda defeats the whole anonymous superhero thing”. Cue both MJ and Webb-Verse remarking that that’s exactly what he earlier said.
  • In Doctor Strange in the Multiverse of Madness, the titular character tells a variant of himself about the death of his sister Donna as a child to convince him that he’s the real thing as it’s something he never talks about to others.
• The Matrix Revolutions:
  • Bane (whose mind has been overwritten by Smith) reveals himself to Neo by addressing him as "Mr. Anderson" in his usual mocking tone three times. Neo is slow to catch on, if only because of how inconceivable it is to believe Smith is walking around in the real world using another man's body.
  • Happens again in the final battle when Smith says, "Everything that has a beginning has an end, Neo" — revealing that the Oracle is still in there somewhere.
• The climax of Muppets Most Wanted involves Miss Piggy almost marrying Constantine, a master criminal impersonating Kermit. When the real Kermit crashes the wedding, Miss Piggy comes up with a way to distinguish them: she asks each in turn to marry her. Constantine confidently says 'Yes, I will! Let's go right now!', while the real Kermit stutters awkwardly and tries to duck the issue.
• In No Name on the Bullet, Reeger first gets paranoid that Gant is after him (or at least knows something about his past that he'd rather not discuss) when Gant calls him 'Dutch' the first time they trade words. When Reeger's fellow card players question him about this, he's quick to change the subject.
• The phrase "As you wish" in The Princess Bride is the Former Trope Namer. Westley, Buttercup's love, has been presumed killed, but turns up as the Dread Pirate Roberts, and Buttercup recognizes him by his use of the phrase which, for him, meant "I love you." For bonus points, he gives her vague hints at first, and when she tells him "You can die too for all I care!" as she pushes him off a cliff, he shouts it as he rolls to his (apparent) doom. (This leads to a My God, What Have I Done? moment for Buttercup. She and Westley both get better.)
• Nickelodeon's original movie Rags, a Cinderella-esque story, has the protagonist (a Cinderfella) meet with the music star (equivalent of princess) at a masquerade ball, and on his way out he tells her, "Be you." Later, when she seeks his help to track down the mystery singer Rags, right before the auditions start he repeats his earlier line, inadvertently revealing himself and later saving himself from having his Secret Identity and big break stolen by his evil stepfather and stepbrother.
• On Chesil Beach: The film jumps to 1975, where Edward is working at a record shop. A young girl asks him for a Chuck Berry record, and when she explains her reason for wanting it, Edward realizes the girl is the daughter of his old love Florence. The girl tells him that her mom thinks Chuck's music is "merry and bouncy," something Florence used to tell him.
• In Ransom, Tom Mullen knows for sure Jimmie Shaker is the mastermind when he hears him say "Shouldn't be a problem": a phrase he heard over and over when an FBI analyst was examining a recording of an earlier conversation between Tom and the kidnapper.
• Happens twice in the original RoboCop (1987), one of which is non-verbal. Lewis initially recognizes Robo as Murphy when he spins his pistol by its trigger guard in the precinct firing range, a trick Murphy had copied from his son's favorite TV show. Later, Robo confronts Emil, one of Boddicker's gang members and repeats the same line with which he tried to arrest the goon the first time around, which freaks Emil out to no end.
  RoboCop: Dead or alive, you're coming with me.
  Emil: (disbelieving) Wait a minute, I know you... you're dead. We killed you! We killed you! WE KILLED YOU!!
• The Secret (2007): Ben is convinced that Hannah is really in Sam's body due to her relating anecdotes from their past and speaking the way that she did. At first he just thinks Sam must have heard it from Hannah, but soon accepts that it's really her.
• In The Sixth Sense, this is how Cole demonstrates his medium powers to his mother, by repeating several things that only his grandmother's ghost would know.
• In Spies Lies And Naked Thighs, a man is introduced as a secret agent who has been surgically altered to resemble an old friend of the main characters in order to stop an assassination attempt on two world leaders. Late in the film, one character who knows that the assassin is hiding nearby manages to tip him off with a signal from college which meant "There's a girl in the room", revealing that this agent is really the old friend.
• In The Ten Commandments (1956), Moses calls Master Builder Baka "Master Butcher" after he's willing to see an old woman killed rather than momentarily pause a construction project. Later on, while disguised as a Hebrew slave, Moses sees Baka whipping Joshua and attacks him, putting him in a choke-hold while calling him "Master Butcher." Baka has a brief Oh, Crap! moment of realization before he's strangled to death.
• Terminator 2: Judgment Day: In a Meaningful Echo to what Kyle Reese said to Sarah in the first film: "Come with Me If You Want to Live."
  • A darker example for Janelle, John's abusive foster mother. "Something's wrong, she's never this nice."
• In Terminator Genisys, at one point Kyle and Sarah are separated from Pops (the friendly Terminator) and wonder if he's not being impersonated by the shapeshifting T-3000 when they reunite. However, Pops' wordy and technical explanation for why he can't shapeshift immediately convinces Kyle that he's the real one.
• Amusingly invoked by Malone in The Untouchables (1987) despite the other person being a complete stranger:
  Eliot Ness: Wait a minute! What kind of police have you got in this goddamn city, huh? You just turned your back on an armed man!
  Malone: You're a Treasury Officer.
  Eliot Ness: Yeah, how do you know that? I just told you I was!
  Malone: Who would claim to be that who was not?
• Wild Things. Cops are doubtful of a young woman's claim that her guidance counselor raped her, due to her promiscuous, troublemaking reputation. But they believe her when not only does another victim come forward, she reports the identical Post-Rape Taunt that the first victim did—"no little bitch can ever make me come".
• In Wonder Woman (2017), Diana realizes that British politician Sir Patrick Morgan is actually Ares— the God of war and the film's Big Bad— when he reveals himself by saying, "You were right, Diana. They don't deserve our help. They only deserve destruction", something only Ares would say.
• In the first X-Men movie, Wolverine has just dispatched the shapeshifting Mystique and is confronted by a suspicious Cyclops. When challenged to prove that he is himself, he calls Cyclops a dick. Given that the pair had squabbled all throughout the film, Cyclops accepts this as proof.