Something Only They Would Say / Fan Works

• Abraxas (Hrodvitnon): This happens a couple times with Monster X in regards to half of it being an Inhuman Human Vivienne Graham. It's Played Straight when Monarch become aware of this and Madison asks it a series of questions only Vivienne would know the correct answers to. Later, Susan is convinced of the truth about Monster X when she hears San and Vivienne's respective voices reciting the Elder Futhark and Frere Jacques, both of which are associated with Vivienne on a personal level in the story.
• The Victorious time travel AU fic "Across the Years" features a variation of this when time-traveller Jade brings Tori from her home time of 1869 into the present to save her life. Jade went back in time to save Tori's life after discovering Tori's diaries and learning that her arranged marriage to Beckett Oliver would be emotionally unfulfilling and end with Tori having a stillbirth and dying. Although Jade's time in the past led to Tori making new diary entries, Jade retains access to the original diaries that record the history that unfolded before she went back in time. When reading the original entries, Tori observes too many of her own writing quirks, ranging from her handwriting to particular turns of phrase, and concludes that the entries she doesn't recognise couldn't have been faked.
• In The Amazing Spider-Man: True Purpose, Spider-Man’s sense of humour is basically his business card, with everyone from old friends such as Logan to newer acquaintances like Hope Summers immediately concluding that they’re addressing the real web-slinger (even when he was apparently dead) when he makes a particular kind of joke.
• And So We Fight has Impa immediately figuring out Sheik is Zelda through the song she played.
  Impa: I know that song because I taught it to you, Zelda.
• Inverted in chapter 9 of the Ace Attorney fic Be Careful What You Wish For where Apollo has to convinces his sisters Diana and Thalia that he isn't their Apollo but rather from an alternate universe where their father Jove Justice died before the two girls were born. Diana asks him what did she say during her bottom surgery while Thalia asks when is her birthday. The fact that he genuinely can't answer them and that their Apollo couldn't make such a joke with such sincerity makes them believe he is telling the truth.
• Subverted in Hard Reset: In an early loop while engaged in a Beam-O-War with Celestia, Chrysalis (as Celestia) convinces Twilight she's the real one by telling her to attack them both, knowing Twilight would believe this is something only the real Celestia would say.
• Dæmorphing: When Toby and the Animorphs investigate the Ralek River, they ask each other questions to make sure the others aren't the ship's Andalites in morph.
• In Escape from L.A., Tom morphs into Jake, and tries to convince Marco that he really is Jake by sharing anecdotes of events that Marco doesn't know Tom was around to witness.
• After Doopliss swaps bodies with Mario in chapter 43 of Paper Mario X 2, the real Mario is left alone with the pig who has been following the team — who is revealed to be Kirby. Kirby is relunctant of joining Mario, asking for proof that he's the real deal. Mario then brings up the ending of the first Paper Mario X to Kirby (triggering a flashback in the process). Kirby then claims that only the real Mario would remember their goodbye.
• In Supernatural fanfic series "Sky Verse", Sam, Dean and Castiel realize they are vulnerable to impersonation and being tricked into an ambush by their enemies due to their use of cell phones to arrange to meet so they agree on passphrases they must use at the beginning of each phone call which are things they would never normally say and which their enemies would not be able to guess.
• In chapter 6 of The Sweetie Chronicles: Fragments, this allows Sweetie Belle to figure out that Elusive is Rarity.
• Subverted in chapter 47 of Variant Strain, where MJ tells Hank in Peter's body that telling her something only the two of them would know isn't enough because she knows about the memory-sharing thing.
• In Turnabout Reunion, the way Phoenix realized he was talking to Rainbow Dash was due to her calling him Nix, the same nickname she gave him when they first met.
• Eugenesis: Galvatron is trussed up in a room, and hears a person who sounds uncannily like Optimus Prime telling him to tell the Autobots what he knows, and then he will be let free. Galvatron eventually talks, and is released and told he can go. This is when he realises that is Optimus, because no other Autobot would ever let him go free. The problem is Optimus is supposed to be dead.
• Ripples, Waves, Tsunamis: When Nami's memories finally break through to the surface, this is how she confirms her identity to Raijax, and vice-versa.
• The God Empress of Ponykind; Celestia realizes just who she's fighting when Nightmare Moon calls her "Emperor". Tzeentch is the only being of Chaos who ever called her "Emperor" instead of "False Emperor", "Corpse God" or "Anathema".
• Played with in Background Pony. Every time Spike has "met" Lyra, he says, "Dig the swell hoodie." Until Chapter XVI, because it's really Discord in disguise. She doesn't realize it until it's too late.
• In chapter 65 of the Turnabout Storm novelization, Maya is channeling Trixie's grandfather, changing herself into a pony in the process. Trixie is completely unimpressed and calls the whole thing a fake, unless she gets proof that she is indeed talking to her grandfather. What Shadowmoon the Illustrious tells Trixie afterwards proves it, since only he and Trixie knew about it until then.
• Inverted in Memoirs when the only way Akagane can prove he's not a figment of the protagonist's imagination is to say something so ridiculously out-of-character that the protagonist realizes his imagination could never have come up with it.
• In Midnight Star: The Frozen Empire, Chrysalis's secret that all changelings are actually her children is something that she has kept hidden for millennia. When Midnight Star reveals this fact to her after explaining her own past, it convinces Chrysalis she's telling the truth as her counterpart would have been extremely desperate to even think of telling it to a pony.
• Bring Me Back Home has a subversion: when Ladybug goes ice skating with Chat Noir, he gives her the same instruction that Adrien gave Marinette a few hours earlier: "Just step, step and glide." She picks up on it and asks if it's a common thing to say. He says it is, so she doesn't think any more of it.
• In Lady Luck (Miraculous Ladybug), this ends up being the reason why there's no Mutual Masquerade between Lady Luck and Chat Noir like in the canon series. During her first outing with the Ladybug Miraculous, Chloe ends up tangled up Chat Noir and hears him joke about their situation. She guesses that he's Adrien from his puns and snarks at him for it, only to see that he's now Chat Noir. Likewise, Chloe's Lame Pun Reaction cues Adrien who she is, meaning both of them know the other's super-hero identity before the glamour could prevent recognition.
• In Time Fixers: Nicktoons of the Future, SpongeCog breaks into HQ after disguising himself as Timmy and his ruse is broken when he agrees with Jimmy that science is always the answer. When the adult Nicktoons are searching the place for him armed with weapons, Jimmy and Timmy, and Danny and SpongeBob run into each other and ask questions such as "What was the first insult Timmy called Jimmy when they met?" and "Who was the one who defeated the Syndicate's Doomsday Device?"
• In How the Light Gets In, Laurel is suddenly and inexplicably resurrected. While Dean, Oliver, and Sara all quickly decide it really is her, Felicity insists they test her somehow. She initially decides to do it by offering Laurel a glass of wine, only for Sara to flip out insisting with the trauma she's been through, that's unacceptably cruel. Dean eventually settles on this:
  Dean: Laur, imagine it's the Superbowl. The Seahawks are playing. We're throwing our annual party.
  Laurel: We throw amazing Superbowl parties.
  Dean: Everything's going great. And then I tell you I'm rooting for the other team. What do you do next?
  Laurel: (disgusted) I immediately file for divorce. ^note This is a sort of Actor Allusion, as Katie Cassidy who plays Laurel is a diehard Seahawks fans.
  Dean: That's my girl.
  Diggle: Well, sounds like her to me.
• In Heart of the Inferno, the third part of The Heart Trilogy, Smaug meets the aged Bilbo Baggins in Rivendell and sneaks in the hobbit's room in his human form. Though Smaug makes blatant references to their first meeting, Bilbo (who has never seen Smaug in his human form) doesn't recognize him until Smaug calls him "thief in the shadows".
• Innocence and Experience has Robin using a very distinctive slang word in front of Tim Drake, who's familiar with Dick Grayson and heard him dropping this very same word. Whoops.
• Rei regaining all her lost memories in Advice and Trust is marked off by her calling Kaworu a "stupid fish". Notably, many of the memories shown feature Kaworu referencing The Princess Bride.
• In the Beast Machines fic "The Dinobot Saga: Episode 1", Rattrap realises that the newly-reformatted transformer is Dinobot when he initially assumes that he's in a "Maximal torture chamber", which reminds Rattrap of the last time someone made that assumption.
• In A Colder War, the true nature of the entity possessing astronaut Shipley is confirmed when he describes the super-soldier serum as enhancing everything within the subject, a description that would only be known to Steve’s closest friends and HYDRA as most modern sources on the serum describe it in a more scientific manner.
• "Finding Peace" is a complex version of this when the Donatello of the 2003 Teenage Mutant Ninja Turtles series finds himself in the "Last Ronin" reality after the final battle with Hiroko Oroku. When talking with the April of this world, Donatello admits that he can't prove his identity to April as he's seen enough to be sure he's from an alternate reality to this one, meaning that there's no guarantee his DNA would be the same as his counterpart and he can't share a story from their shared past as there may be differences he can't anticipate. However, April decides to believe him on the ground that his response was "a classic Donatello overthink", basically deciding that only Donatello would come up with such an elaborate analysis of the current issues in their situation.
• In On the Run, Dom Toretto starts to suspect Clark Kent is more than he seems when Clark mentions how “a real driver always knows what’s in his car”, advice that Dom received from his father and passed on to those close to him such as Vince and Letty (Clark received that advice from Letty after he saved her life).
• In Blank Slate, when Professor McGonagall learns that James and Lily Potter have been alive but amnesiac for the last fourteen years, Remus and Sirius accompany the next group of visitors to 'test' them; Sirius initially visits as Padfoot, with James confirming his identity when he yells at the dog to "Transform and use your damn words!" when Padfoot keeps barking at him before anyone tells them that the dog is a person.
• Hiccup in Persephone manages to get Stoick’s attention by telling him that his mother/Stoick's wife is alive. At first Stoick thinks it is some underhanded trick, but he slowly starts to believe him when Hiccup draws him a portrait with too much detail for him to falsify. They strike up a deal; Hiccup escorts him to Valka’s location, Hiccup can hold off on telling him where the Red Death’s nest is and Stoick spares Astrid and Toothless until then.
• Batman spends the first half of Batman: Melody for a Mockingbird drawing a blank for who is trying to destroy Bruce Wayne's life. Finally, the mystery man mentions Cloak and Dagger, a Calvin-ish board game Bruce made up as a kid. It brings Bruce to an instant realization this is his childhood friend and the game's co-creator, Tommy Elliot.
• SOSchip:
  • oghond has never seen LF's face in pictures, or heard her voice. In the first chapter, when LF first appears, oghond does not recognize her due to this reason. That is, until LF speaks, using words that would be Sesquipedalian Loquaciousness for a German learning English. It's her sophisticated manner of speaking that allows oghond to realize who it is.
  • Two chapters later, in "A Coder on Board," oghond's best friend Absent is turned into an Oshawott. Upon waking up and realizing he is now a Pokemon, oghond at first doesn't recognize him, but does think he sounds somewhat familiar. She just can't place the voice until Absent turns to HP - who just saved his life - and remarks "Pride yourself." As oghond puts it:
    And all at once the identity of the person clicked with those two words.
    My eyes widened in recognition.
    There was only one person I knew who said "pride yourself" in that way. Which is odd, considering that the phrase itself is pretty common, but here's the rub: no-one else I knew who had said that phrase said just that phrase.
    No one else except...
    "Absent?" I gasped.
  • Two chapters after that, in "Hostile California," it's Absent who does this- twice, both times to members of his family and both times in order to prove his identity after having been turned into a Pokemon. The first time he does it, it happens as soon as he enters the house. His mother and brother, Nathan, do not recognize him at first- until Absent notices the family dog. Almost immediately, he calls out "Come here, stupid!", causing the dog to stop glomping his brother and start glomping him. The reason it counts as this trope? Only a member of the West family (and oghond, but that doesn't matter here) knows that the dog answers to both her real name and "stupid." With Nathan already in the house, there's only one possible conclusion as to who the Oshawott at the door could be...
  Absent's mother and Nathan (shocked): CORBIN?!
  • Later on, he does it again to his father, who- despite having heard his voice on speakerphone- is still slightly disbelieving as to the fact that his son is an Oshawott. This is until Absent apologizes for failing to "bequeath unto [his father] that boot to the head." It's a Mythology Gag— the real Absent once showed his father a video called "Last Will and Temperament," in which... well, see for yourself.
• In Sword Art Online Abridged, Healthcliff gets exposed as Kayaba because of his fascination with pop culture references nobody else gets (and how he makes a Call-Back to something Kayaba said back in episode 1).
  Heathcliff: Oh, so now you've seen TRON!
• A meta-example in Persona 5: Hoshi to Bokura to, when Akira first wakes up in the Velvet Room, the line Igor greets him with confirms to the readers, that in this version of events, Yaldabaoth did not seal away Igor and impersonate him.
  Igor: Welcome to the Velvet Room, my dear young man.
• In The Power of the Equinox, the canon example from the second season finale of My Little Pony: Friendship Is Magic is made mutual. Dimmed Star (the recently transformed Twilight Sparkle) is on the verge of killing Princess Cadance in hateful fury, unaware that the Cadance who imprisoned her in the underground caves is an impostor. Wanting to die with happy memories in her mind, Cadance starts reciting the song she and Twilight used to sing. Dimmed Star stops in her tracks and continues the song, after which both mares finish it in unison. This leads to Cadance realizing that the monstrous mare who almost ate her is actually Twilight, and Dimmed Star learns that she's been dealing with an impostor of her former foalsitter.
• A Diplomatic Visit: In chapter 5 of the second sequel, Diplomacy Through Schooling, when Pharynx sees where Thorax has led them for his bachelor party, he thinks this may be an impostor... until Thorax whispers something to him that convinces Pharynx of his identity.
• An unusual variation in Canary's Wrath. Oliver sees Laurel kill Damien Darhk, talks with her, learns she's the Spectre, and kisses her. Shortly after she leaves, he's informed she also killed Malcolm Merlyn. It takes hearing that, for him to conclude yes, that was definitely her.
• Played for Laughs in Shadow Realm: Fifteen. Tessa is faced with two versions of Fifteen, one of which is the shapechanging Copycat, and has a gun with one bullet. She first asks them to say something only they would know, only for both to give an acceptable answer. She then asks for the name of her boss, only for both to give the correct answer at the same time. Finally, she asks them what her number is. One yells, "How the hell should I know?" while the other says it. She shoots at the one who didn't give an answer, only for him to use the other Fifteen as a Human Shield. The human shield turns back into Copycat and dies, and the real Fifteen points out that Tessa has never actually told him her number.
• In A Pairing Of Souls, Shen Qingqiu convinces people he reverted to his pre-qi deviation persona when he starts spouting insults and sneering at Luo Binghe and Liu Qingge (respectively "beast" and "brute").
• In Queen's Checkmate, Futaba demands proof that the being talking to her is a part of her (specifically her Shadow). Shadow Futaba responds with an Among Us meme, which is enough to convince Futaba.
• Ma'at: To confirm Dani's identity after a Super Gender-Bender:
  She should be able to convince Dominic or Gunther of her identity. They'd been on enough digs that one or another of the near-blackmail stories they had on each other should overcome their disbelief.
• The Reaping of Hatsune Miku (Vocaloid & The World Ends with You): After coming Back from the Dead, Luka goes to meet with her friends and needs to convince Meiko that it's really her. Her high-school sake stash and chocolate orders aren't sufficient, so she tries something... a little more personal.
  Meiko: (muffling her) Oh my god you're Luka.
  Len: Collection of silver what?
• Rebloom: White Lily Cookie confirms her identity to Licorice and Poison Mushroom Cookie by telling them that her favorite tea blend is matcha tea — not because she likes the taste (she actually hates it) but because the smell reminds her of her sister. And then immediately Played for Laughs with Pomegranate Cookie; when Licorice Cookie questions her identity, she just smacks him upside the head, which he accepts as proof she's genuine.
• In one chapter of the Harry Potter fanfic The Problem with Potions, Snape knocks on the door of Grimmauld Place, but Harry doesn't open it for him, unsure if it's really Snape.
  Harry: How do I know you are who I think you are?
  Snape: I think you are a complete dunderhead.
  Harry: That's not good enough. Anyone who was Snape's student could give that answer.
  Snape: I hate your father.
  Harry: Still not good enough. But you're getting closer.
  Snape: I once took your Quidditch book. When you went to get it back you saw my leg was bitten.
• The Animorphs fic "The Salvation" starts shortly after the last book of the series, with the deceased Rachel being brought back to life in the body of the brain-dead Melissa Chapman. When her initial attempt to reunite with Tobias fails because he can't accept her claim to be Rachel, she is later able to convince Cassie of her identity when she mentions a time she helped Cassie buy Jake a present that Cassie threw away because she was embarrassed, and Jake is later persuaded of her identity when she makes a speech about how she only came back because Tobias needed her. Once Rachel reunites with Tobias, he accepts that she's Rachel for the non-verbal reason that nobody else would know how tightly a grizzly bear can carry a red-tailed hawk without causing the hawk any damage.
• In Dazed and Confuzzled, when Jaune checks the book that kickstarted the plot (a self-published trashy romance novel by a Saffire C. A.), he realizes the description of one character is very familiar... and then he finds the word "unconscious" written "unconcious". There are only two people he knows that write that word like that, and one of them (Nora) is clearly not the writer - the other being his sister Saphron Cotta-Arc.
• You will always have a part of me nobody else is ever gonna see: In chapter 21, Noriaki Kakyoin needs to prove himself to Jotaro, Josuke, and Jolyne as the real and alive 36-years-old thanks to Jotaro warning what he thought was a memory from 1988 Hong Kong instead of a memory construct or an illusion by an enemy Stand-user. He gets through by describing the night after Jotaro defeated him and removed his flesh bud, with enough details to convince the marine biologist. In an Inverted example, Kakyoin realizes that Jotaro and the other Joestars are from an Alternate Timeline when Jotaro doesn't remember the bone cancer the former dealt with right after Egypt.