Something Only They Would Say / Live-Action TV

• In an episode of 3rd Rock from the Sun, Dick gets locked in the stairway of a dentist's office because he is so desperate to smoke a cigarette. When Harry finally finds him, he shouts through the door:
  Harry: Dick?
  Dick: Harry?
  Harry: Wait, how do I know it's really you..?
  Dick: It's really me!
  Harry: Well, that's something you would know!
• Agents of S.H.I.E.L.D.:
  • In the Season 1 finale, the message to Mike Peterson from his son to let him know he's been rescued includes something only they would say to prove it isn't a trick.
  • In Season 5, Deke, a man from the future, recalls a phrase his mother would always say to him, which she claimed her mother would always say to her. Towards the end of the episode he hears Simmons say it, and realizes that she is — or rather, will be — his grandmother.
• Arrested Development:
  • When Oscar has to convince Michael that he's not his twin brother George Senior:
    Michael: No, no, don't buy it. I'm taking my son to the cabin, and there's nothing you can say to make me believe that you are not my father.
    Oscar: I understand. Your child comes first.
    Michael: Oh, my God, you're Oscar.
  • When Buster is pretending to be George Senior and refers to Lucille as "mother":
    GOB: Mother?
    Buster: I mean lover. I love making love to mother. I mean lover.
  • And the mysterious pimp "Frank":
    Michael: She's a...?
    "Frank": Lady of the evening. Working girl. She turns illusions for money.
    Narrator: And that's when Michael recognized the voice.
    "Frank": ...Tricks!
    (Michael fumbles for the lightswitch)
    "Frank": Don't you do it! Ain't nobody gonna see what Frank look like!
    (Michael turns on the lightswitch, revealing none other than Gob, and his ventriloquist dummy Franklin)
• A meta-example in Babylon 5: G'Kar has a vision of an angelic being (in the form of his late father) telling him that it's up to him and his fellow Narns to break the cycle of violence between themselves and the Centauri, or both sides will be destroyed. G'Kar asks "Who are you? Where have you been all this time?" The response comes: "I have always been here" — and that's when the audience realises the angelic being is actually Kosh.
• Interesting variation in the final episode of Blackadder II. Blackadder has apparently sold out Queen Elizabeth to a master of disguise for a single key bit of information — in this case, Nursie's habit of dressing up as a cow at dress-up parties.
  Blackadder: From this moment he was doomed. For you see, the prince is a master of disguise, while Nursie is an insane old woman with an udder fixation.
• Buffy the Vampire Slayer:
  • In the episode "Dead Man's Party", Cordelia asks, "How do we know it's really you and not zombie Giles?", to which Giles responds, "Cordelia, do stop being tiresome," and Cordelia quips, "It's him."
  • In the fourth season, Faith attacks Buffy in her home and activates a magical device during the ensuing fight. Afterwards Joyce asks her daughter if she's all right, and "Buffy" answers with Faith's Catchphrase ("I'm five by five"), letting the viewer know that a body switch has taken place. Later on in the episode, Buffy (in Faith's body) makes reference to the aforementioned episode of Giles-turned-Demon to prove to Giles it's really her. But not before playing with the idea:
    Buffy: Giles, it's me, and I can prove it. Ask me something only Buffy would know.
    Giles: ...who's President?
    Buffy: We're checking for Buffy, Giles, not a concussion.
  • Similarly, in the fourth season of Angel, Angel realises that Cordelia is possessed by the same power that is controlling the Beast when both use the endearment "my sweet".
• Cheers: In the series finale, the gang are watching the Cable ACE Awards on TV and find Diane's won one of the categories. They're initially uncertain it's Diane until she starts making a speech, and just keeps talking.
  Frasier: Oh, boy is it her...
• Cold Case:
  • An episode has the detectives trying to deduce who planted a bomb that killed a married couple by interviewing the friends who had visited them the weekend before. It soon became obvious that the supposedly dead wife was in fact alive and pretending to be one of the friends in question (they bore a strong resemblance to each other)—it was the friend who died in the blast along with the husband—when one of the other friends mentioned hearing the wife say something very similar to what the woman had told them.
  • In another episode, they deduce who the killer is when they realize that the inscription on the victim's tombstone is a Bible verse that one of the suspects quoted to them.
• In the Community episode "Conspiracy Theories and Interior Design" Jeff recognises that only the Dean could possibly have written Garrity's ridiculous lines.
• Criminal Minds: In "Revelations", the unsub has Reid hostage and is streaming the video to his fellow members of the BAU. When the unsub demands that Reid pick another member of the team to kill, Reid chooses Hotch, calling him a "classic narcissist", then quotes a Bible passage. The rest of the team thinks that Hotch takes this personally, but in fact he's analyzing everything Reid says for clues to his location; Hotch is well aware of his own flaws, and also knows that narcissism isn't one of them. He then looks up the Bible passage Reid quoted and discovers that Reid quoted it incorrectly, something which Reid, who has an eidetic memory, would never do. The correct Bible verse turns out to be the key to where Reid is being held hostage. Reid even tells Hotch after his rescue that "I knew you'd understand."
  Hotch: Alright, everybody, right now — what's my worst quality? ...I'm all these [flaws], but none of you said that I ever put myself above the team because I don't, ever. Reid and I argued about the definition of classic narcissism and he knew that I would remember that, and he also quoted Genesis, chapter 23, verse 4 — read it. ...He wouldn't get it wrong unless it was on purpose.
  Morgan: He's in a cemetery.
  • In another episode, an unsub who grew up in an abusive foster home decides to pick two current residents up from school and talk to one of them as part of his final revenge plan. Since the kids have never met him, they're skeptical about his tale of having grown up in the same home... until he asks them if the "mother" still wears the key to the (always-padlocked) refrigerator around her neck.
• Doctor Who:
  • "The Enemy of the World": The Second Doctor intends to prove to his companions that he's not the Identical Stranger villain Salamander by playing his recorder ... only he left it in the TARDIS, so he mimes playing it.
  • In "The Christmas Invasion" and the "Children in Need" mini-scene that leads up to it, the Tenth Doctor demonstrates himself to be the same man as his previous incarnation by repeating to Rose the first thing he said when he met her in his previous body.
  • "Midnight" has a strange "detect the enemy" variant on this: An alien being seems to possess a woman, and it keeps repeating whatever anyone says to it. The Doctor surmises this is its attempt at learning. Then it says things at exactly the same time as everyone else. Then it only does for it the Doctor. Then it speaks before the Doctor does... Eventually, the woman seems back to normal, and the Doctor seems to be possessed. The woman convinces everyone else to throw him out the airlock... but two characters realize the being has just stolen the Doctor's voice and is still possessing the woman when she uses two phrases the Doctor used earlier ("Molto Bene" and "Allons-y").
  • "Turn Left" has the reappearance of "Bad Wolf" (series one's Arc Words) as a message from Rose to the Doctor, letting him know that holes must be opening between their parallel universes, which is very very bad.
  • River Song has her personal way of calling the Doctor for help: graffitiing a significant historical artifact with her current space-time coordinates, along with "Hello Sweetie".
  • "The Impossible Astronaut": The Doctor becomes suspicious of his companions behavior when they refuse to tell him about his future death at Lake Silencio. In order to prove he can trust her, the Doctor demands that Amy swear by something that matters.
    Amy: Fish fingers and custard.
    The Doctor: My life in your hands, Amelia Pond.
  • When the Doctor hears the phrase "Run, you clever boy, and remember", he knows he's found Oswin/Clara again. Twice.
  • "Nightmare in Silver": Clara Oswald asks this of the Doctor while he's fighting a Battle in the Center of the Mind. The Doctor starts admitting he's always been attracted to her, only to get a slap which puts the Doctor's real personality back in control. As Clara points out, even if he did feel that way, he'd never admit it to her. Later, she asks the Doctor if he thinks she's pretty, and he insults her, satisfying Clara that it's the Doctor in control.
  • Inverted in "The Night of the Doctor". As the 8th Doctor attempts to drag a woman to safety in the TARDIS, his assurance to her that it is Bigger on the Inside instigates a full-tilt freakout when she realizes that he is a Time Lord.
  • "Dark Water" plays it for drama. After Danny Pink is killed, the Doctor and Clara travel to what may be the afterlife to get him back. However when Clara is put in verbal contact with Danny the Doctor is suspicious, and urges Clara to ask Danny something only he would know. Danny however is afraid that Clara, if convinced, will kill herself to be with him (unaware she's there physically) and manipulates her into closing the channel between them, something only the real Danny would do.
  • "Thin Ice": The Doctor isn't sure if a particular nobleman in 1814 London is actually an alien in disguise. The mystery is quickly solved, however, when said nobleman is shocked to see Bill (who is black) in his house and demands "that thing" leave. Both the Doctor and Bill immediately agree that an alien wouldn't care about skin colour; that level of knee-jerk racism is exclusively human.
  • "It Takes You Away": While trying to find out if the Grace in the Alternate Universe is real, Graham asks her to tell him about the frog necklace he's wearing. She remembers it perfectly, making him that much more reluctant to believe she's a fake.
  • Deconstructed twice over in "Wild Blue Yonder":
    • The Doctor and Donna attempt it, but quickly realise a flaw; if it's something only one party would know, how is the other supposed to know it's true? And since the problem they're dealing with has their memories, they can't share something only they'd both know.
    • At the climax, the Doctor is faced with two Donnas, and asks them to describe why her childhood teacher's name was funny. One Donna gives an overly-analytical explanation and the other goes "it just is". That's the one the Doctor goes with. Leaving the real Donna behind.
• On Dr. Quinn, Medicine Woman, a visiting naturalist rapidly befriended the title character and her beau Sully. To that end, they all attended Horace and Myra's wedding, at which point Horace revealed that Dr. Mike and Sully have just gotten engaged themselves. Stunned, the man proceeded to offer the happy couple a toast, which includes the recitation of a beautiful poem, leaving Mike just as stunned, as the poem was precisely the one her presumed-dead fiancé recited at their engagement party. When she confronted him, after some badgering, he finally admits that he is in fact, the man in question.
• Eureka:
  • The episode "Jack of all Trades" has Jack swapping bodies with the Astreus's crew, starting with Fargo. At first Alison thinks Jack has gone crazy, and when "Fargo" corroborates, that he's playing along as some sort of joke. Then Jack tells Alison they were just making out, leading to this:
    Fargo (in Carter's body): Dr. Blake, PDA in the workplace is against GD policy...
    Carter (in Fargo's body): Bigger! Issues! Fargo!
    Alison: Oh my God, you're not kidding.
  • When Jack shows up just after a Jack impostor tries to kill Zane, Jack's attempt to explain how he got there tips off Zane to the fact that he's telling the truth.
    Zane: No computer simulation of you could be that incoherent.
• Elementary:
  • Variant: Watson asks someone who claims to be looking for Sherlock, "Are you a friend of his?" "He doesn't have any friends" is the right answer.
  • An earlier episode also has an inversion. Holmes figures out who the killer-of-the-week is, but ends up being kidnapped. Earlier, Watson is shown to be frustrated about Holmes texting like a "teenager on a sugar high" with tons of unrecognizable abbreviations and emoticons (Holmes believes it allows for efficiency in communication). When the kidnapper tries to tell Watson that everything is fine, she uses Holmes's phone but texts in a normal manner. Watson immediately goes to Captain Gregson. After he's freed, Holmes tries to get credit for "deliberately" getting the kidnapper to text Watson.
• A character missing this was used in one episode of Family Matters, an episode that saw Steve Urkel bust a criminal and receive a death threat from his brother. This results in Carl and a fellow cop taking shifts in protecting Steve. For years, Carl had always said, "See you later," to that particular partner, who would always reply, "Not if I see you first." Later in the episode, when Carl left his watch, the "buddy" turned out to be the killer in disguise, but as he's about to kill Steve, Carl busts in with the police force and arrests him. As it turns out, the killer replied to Carl with a simple, "Yeah, see ya," letting Carl instantly know it wasn't him.
• Farscape: In "A Human Reaction", John Crichton crashes back to Earth and is immediately detained by the military who refuse to believe he's the real Crichton and not an alien impostor. Crichton's father eventually gets in to see him and asks John to tell him what they did for his tenth birthday. When John is able to finish the story they finally believe he's who he says he is. It eventually turns out that the whole trip back to Earth was a simulation and "Jack Crichton" is an alien who only knew the story about John's childhood from scanning his memories.
• A recurring bit of Father Dowling Mysteries was Frank having to deal with his twin brother, Blaine, a con artist who often posed as his priest brother for scams. The two are arrested together while dressed alike as Sister Steve is asked to figure out who's who. She asks Frank what a patron told him in confession and Frank says he can't repeat it. Steve knows it's him as Frank would never break the sanctity of confession, even to save himself.
• In the F Troop episode, "Wilton, the Kid" an outlaw called Kid Vicious, who is a dead ringer for Capt. Parmenter comes to town. In the climax, Kid dresses up Parmenter and ties him up claiming he caught the imposter. The others quickly realize off that the one tied up is the real Parmenter when he he trips and falls.
• Frasier:
  • When Maris goes missing for several days, Marty has police check her bank details. They find several of her cards have been spent in New York boutiques, but it's not until they confirm none of the purchases have been spent on food that Niles realizes Maris is safe. Then Frasier points out Maris is safe and hasn't bothered contacting him for several days while she went on a shopping spree.
  • A later episode has someone delivering mystery gifts to Niles. He's uncertain it's Maris, who he's in divorce proceedings with, until an incident at Café Nervossa. A barista confirms that an elegant, well-dressed woman came in, and ordered an expensive latte... then took one sniff of it and left. Niles starts having a sobbing breakdown as he realizes that, yep, it's Maris.
• Game of Thrones: When Tyrion sends an offer of alliance to Jon on behalf of Daenerys, he closes with the statement "All dwarves are bastards in their fathers' eyes", a sentiment he shared with Jon back when they first met, in order to prove it's him.
• In an episode of Get Smart, Max is kidnapped by KAOS, who sends a highly-trained impersonator to take his place in Control. When the real Max storms into the Chief's office, the Chief sets up a panel to ask both "Smarts" several questions to decide which is the real one. For example, 99 asks both "Did you ever kiss me?" The fake Max says, "Don't you remember?" But the real Max says, "I'm not the kind of man to kiss and tell." Later it's revealed that the real Chief has been replaced by an imposter, too.
• On one episode of Gogo Sentai Boukenger, we see a case of "Something Only They Would Do": an imposter has disguised itself as Souta, and the rest of the team must figure out who is the real one. Masumi eventually aims his gun at Natsuki, who is standing directly in between the two, and fires, trusting that the real Souta (who is fully powered up as Bouken Blue at the moment) will protect her while the fake does nothing. He turns out to be right.
• In the Goosebumps TV adaptation of Stay Out of the Basement, Margaret knows which Mr. Brewer is her real father when the real one calls her by her Affectionate Nickname, "Princess".
• In the pilot of Graceland, Mike is on his first serious undercover operation and is ordered by Russian mobsters to kill Donny, a DEA undercover agent who had his cover blown. They end up in a Mexican Standoff and Mike is trying to convince Donny of what is going on but Donny never met Mike and is highly suspicious of Mike's story. Mike tells him that he just moved into Donny's old room in "Graceland", the house the undercover agents share, and that Lauren, Donny's fellow DEA agent, told him not to touch any of Donny's stuff. Since this is exactly what Lauren would have told the New Meat, Donny believes Mike and they lower their guns.
• In one episode of Hannah Montana, Miley's cousin disguises herself as Hannah to reveal her secret to the world. Lilly and Oliver stop her, but they can't tell the two apart. Oliver asks the girls if they want to kiss him. The fake one, who likes Oliver, agrees, while the real one says no.
• Subverted on Haven. A shapeshifter decides to do a Kill and Replace at Audrey's birthday party, and at one point, Audrey is suspected of being the imposter. She rattles off a bunch of personal information, like her favorite music and her middle name, in order to convince her friends she's not. Except she's so new in town that no one knows if any of that information is true. In the end, this Audrey is the imposter.
• In Living Color! parodies this in its fake trailer for Ghost 2. When Sammy Davis Jr.'s ghost tells the medium to relay to his wife he loves her, the wife says "Sammy would never say it like that". When faux-Whoopi tells her "Sh-Boing-Boing-Boooooiiiing", his wife instantly knows his spirit is there.
• In an episode of Jessie, Jessie and Zuri accidentally switch bodies with Ravi's magic bell. When Jessie goes to Ravi for help, Ravi doesn't believe her to be Jessie in Zuri's body until "Zuri" mentions that Ravi still wears choo-choo underwear which is a secret between him and Jessie.
• In the Law & Order universe, to ascertain if someone is an undercover cop, the other cops ask what the color of the day is.
  • During the prosecution of a young woman accused of killing her mother so that she could have her stepfather all to herself, the DA's began to suspect that the girl was telling the truth—that the man had seduced her and killed his wife when she found out and threatened to both divorce him and have him charged with statutory rape. To that end, they called both the girl and the stepfather's new girlfriend into a conference room and gently asked the girl to describe what the man had said and done when making advances to her. The girlfriend's horrified reaction to what the girl was saying cinched it.
  Woman: "That's enough."
  Jack: "Sound familiar, does it?
  • In a Season 21 episode, a supposed heiress is found out when she uses "jughandle" to describe an offramp, exposing her really being from New Jersey.
  • In an early episode of SVU, the detectives realize that a fellow cop is the Serial Killer who's been preying on prostitutes when they interview a survivor and note the way she shielded her eyes when the assailant blinded her with a flashlight (he was holding in the way cops are trained to do).
• In the Lifetime Movie of the Week "Video Voyeur" (Based on a True Story), a woman becomes uneasy as to how her neighbor knows things he couldn't possibly know. In particular, one morning, she declares that she's "having a bad hair day". When she encounters him later, he tells her, "Your hair looks fine!" She searches the attic above her bedroom and bathroom and finds cameras that he's set up to record her and her family.
• In Lois & Clark an identical brush of the hand on her cheek finally (and accidentally) clues Lois Lane in on the fact that her boyfriend isn't just a mild-mannered reporter.
• In Lost, The Man in Black is inhabiting John Locke's body; when he meets Richard, he says, "Hello, Richard. It's good to see you out of those chains," recalling a conversation the two had centuries earlier when Richard was chained to the walls of the Black Rock.
  • In the second season, where Desmond is identified by his use of "brother".
  • Happened in the previous season with the whole Red Sox thing that Sawyer hears Jack say (Sawyer heard it before from Jack's father, that even mentioned that felt bad and wanted to call his son).
• Marvel Cinematic Universe:
  • Iron Fist (2017):
    • When Danny Rand approaches Jeri Hogarth, she tests his claim that he's Danny by quizzing him about her workspace from when she interned at Rand Enterprises:
      Danny Rand: Look you remember me, right?
      Jeri Hogarth: No.
      Danny Rand: Come on! You were an intern in the legal department at my dad's office?
      Jeri Hogarth: Where was my office?
      Danny Rand: Um...you didn't have one. They put you in the copy room.
      Jeri Hogarth: My desk?
      Danny Rand: Uh, it was a folding table, with a file under one leg because the flooring—it was too uneven.
    • Danny tries this out with the Meachums, but fails because he only gives them basic information that could be looked up online (in Joy's case) or are too stubborn to believe him (in Ward's). He later breaks through to Joy via a shared habit from their childhood regarding brown M&M's, the only color they refused to eat.
  • Jessica Jones (2015) has an inversion of this as Jessica and Trish plan their move to get up close to Kilgrave so that Jessica can kill him. They decide on a code phrase that Jessica will say so that Trish will know that Jessica still is not under Kilgrave's control. They realize that they cannot use something she would normally say because Kilgrave could just make her act like herself (as he just did with Luke), so they decide it would have to be something she would never say. Jessica decides to use the phrase "I love you", which turns out to be particularly handy at the episode's climax.

• In an episode of Murdoch Mysteries a female witness uses the word "huckleberry" to describe anyone she does not consider to be an upstanding citizen. When Murchoch later reviews the transcript of an old trial he discovers that the key witness in that trial also used the word "huckleberry" to describe people she did not like. He quickly discovers that the two witnesses were actually the same woman who was paid by an unscrupulous prosecutor to assume fake identities and act as a prosecution witness so the prosecutor could win more cases.
• Subverted on The Middleman, when Wendy asks MM this and he refuses to divulge secrets through a civilian interpreter. That's good enough to prove it for Wendy.
• NCIS: Los Angeles:
  • A common bit is for the team (or other government agencies they meet) to have specific code phrases for security.
  • A hacker is using intricate software to not only perfectly mimic the team's voices but even "deepfake" video likenesses. Nell calls up Kensi and Deeks, asking them to prove their identities by answering "what's Hetty's favorite tea?" As it happens, neither of them has the right answer but their bickering argument about it is enough to prove to Nell it's really them.
  • By the next season, the team has run into so many "deepfakes" that they create special code phrases that sound like casual conversation. So when Callen answers a call from Sam with "Sam Hanna, greatest partner in the world" and Sam doesn't answer back with "I love you too," Callen knows this isn't really Sam. He calls the real Sam who answers with "G, my main G-man" with Callen giving the proper response phrase.
• In Now and Again, Michael Wiseman, killed but brought back to life by the government in a new body, makes use of this to insinuate to people from his past life who he really is.
• This was also used on NYPD Blue. The "color of the day" refers to a color that undercover officers wear to distinguish themselves from real criminals. If a bunch of cops raid a drug den, they might think twice before getting too rough with someone who's wearing, say, a green shirt if that's the color of the day. If you look at the blackboard behind Sipowicz's desk there's an entry for the color of the day, filled in each morning by Fancy (or whoever). Since NYPD Blue always strove for realism this is probably Truth in Television.
• The Once Upon a Time episode "The Thing You Love Most" has a variation: When Regina attempts to interrogate Mr. Gold about Emma coming to town, he asks her to "please" excuse him. This is the first hint to Regina and the viewers that he remembers his life as Rumpelstiltskin, since it recalls a conversation that they had in the Enchanted Forest: Part of his price to help her cast the curse is she must do whatever he asks when he adds "please" to the sentence. Regina only agreed to that condition because she thought she'd be able to rewrite Gold's memories with the curse.
• When Haley has locked herself in the tutoring center during a school shooting on One Tree Hill, she identifies her husband when he completes their catchphrase through the door ("Always..." "...and forever.") and lets him in.
• Subverted on The Orville. Mercer and Kelly come to a spaceship with a video talk with Mercer's parents who make snide remarks about Kelly (who cheated on Mercer) and ask their son how his colon is doing. When they go onto the "ship", Mercer and Kelly are transported to an alien zoo. It turns out Ed's "parents" were just a hologram created to trick them into boarding the ship. Mercer has to give props to whoever programmed the hologram as that's exactly the way his parents would have acted.
• The Outer Limits (1963) episode "The Architects of Fear" features a poignant example. A man volunteers for a mission to be turned into an alien-like creature, climb inside a fake UFO and launch an "attack" against the earth. (All this as part of a Genghis Gambit by a shadowy organization to bring about world peace by uniting humanity against an external threat.) The plan goes awry however, when the "UFO" crashes and the grotesque "alien" is shot by hunters. The man's pregnant wife (who knows nothing about the mission) arrives on the crash scene and doesn't recognize the ship's alien-looking occupant as her husband—until he does the "mark against evil", a special pointing gesture that has special meaning for the two of them, just before he dies of his wounds.
• Paper Girls:
  • A regular bit of the teens proving who they are to their future selves (or relatives) by reciting stuff only themselves would know.
  • Larry finally believes who the girls are when they matter-of-factly discuss delivering for a newspaper that went out of business twenty years earlier.
• Power Rangers
  • A meta example occurs in Power Rangers Mystic Force: after the heroes' HQ gets invaded, the Mystic Mother complains about having a headache. Just like how Rita Repulsa would do upon her plans being foiled.
  • Small, but very consequential one at the very end of Power Rangers Turbo. General Norquist, commander of the NASADA institution, is informed that a ragged looking kid (Justin, our now-depowered Blue Turbo Ranger) claiming the Power Rangers need their shuttle has been apprehended for trespassing, but he decides to hear this kid out. Whatever Justin whispered in his ear, it involved the name of the planet Eltar. His reaction shows that no one else BUT the Power Rangers would know about that planet and its importance, so he instantly allows four equally ragged looking teens that he's told are the Rangers to immediately take off in their highly advanced shuttle, setting the stage for Power Rangers in Space.
  • In Power Rangers Dino Fury episode "Things Unspoken", Fern had admitted to the Green Dino Fury Ranger that she hadn't been able to admit to Izzy that she loves her when the latter rescued her, not realizing that Izzy was the Green Dino Fury Ranger. When they talk at the end of the episode, Izzy tells her "I love you, too!" and Fern is confused at first until she puts two and two together.
• In Red Dwarf, Rimmer tries to discourage Lister from going ahead with his plan to become Rimmer's superior officer by posing as Kristine Kochanski (who Lister had a crush on and wants to revive as a hologram). Rimmer succeeds in convincing Lister that there's no point in doing it as "she" has no interest in him at all... until "she" says, "I want a man who's going places. Up, up, up the ziggurat, lickety-split!"
  • In "The Inquisitor", after Lister and Kryten are erased from the timeline to make way his "sperm-brother" and another mechanoid, Lister convinces their counterparts of their identities by listing several embarrassing personal details about Rimmer, that only Lister could possibly know.
  • Inverted in "Psirens", a shape-shifting, brain-sucking alien monster gets on the ship and looks just like Lister. The crew try various tasks that only Lister should know but the Psiren can read Lister's mind and so mimics every action perfectly. They finally trick it by giving one Lister a guitar and telling him to play. Lister is normally a Dreadful Musician but genuinely believes that he's an amazing guitarist, so when this Lister plays like the ghost of Jimi Hendrix, they immediately blast it.
• Sabrina the Teenage Witch gets impersonated by her Evil Twin, so her aunts have her say "woo-hoo" to see if she's the real one. Salem doesn't believe her, but Sabrina proves her identity by threatening to tell Zelda about the time he was in her lingerie drawer…
• In the The Sarah Jane Adventures episode "The Man Who Never Was", Luke twice sends a message to Rani and Clyde by unconventional means. Both times he proves it's him by calling them "Clani".
• Conan O'Brien's Saturday Night Live sketch about Moleculo (THE MOLECULAR MAAAN!) has a superhero keep blowing his Secret Identity this way.
• Invoked Trope in Shadow and Bone. When Mal turns up at the Little Palace demanding to see Alina, Kirigan pretends to be skeptical, saying many people are claiming to be friends of the Sun-Summoner just to get a look at her. However surely a childhood friend would know what her favorite flowers were? Mal immediately replies, "Blue irises". It's no surprise we then see Kirigan presenting Alina with a posy of blue irises.
• Sonny with a Chance: When Chad starts using a Doppelgänger stunt double to impersonate him on every "dangerous" date with Sonny, Sonny manages to tell the two apart by messing up both their hair. The real Chad hates having hair messed up and quickly fixes his hair, while the fake one doesn't care at all.
• Stargate SG-1
  • In "Crystal Skull", Daniel Jackson is shifted into another dimension that makes him invisible to everyone but his grandfather, who unfortunately is known to be slightly insane. Daniel instructs his grandfather to repeat some things after him to convince his team that he is standing right there with them. When a skeptical Jack responds in the usual way, Daniel frustratedly mutters "Jack, don't be an ass", which grandpa repeats word for word. Jack is taken aback and after a second he replies, "Daniel?"
  • The situation is reversed in "Fragile Balance", where an infuriated "Daniel!" from a considerably younger version of Jack is taken as confirmation of his identity by Daniel (the two characters usually adopt a particular tone when speaking to each other). The actor who played Young Jack should have gotten an award for the brilliant job he did of mimicking O'Neill's mannerisms and speech patterns.
  • In another case, when Daniel has been body-swapped with an elderly man, O'Neill tests him by asking "Describe for me the dress your sister wore when I took her out last week." Daniel responds "I don't have a sister, Jack... and if I did, I'd never let her date you."
  • The trope is lightly mocked in the episode "Spirits", where they encounter shapeshifting aliens:
    Daniel: Jack. Are you you?
    O'Neill: Yes. Are you?
    Daniel: What?
    O'Neill: Never mind.
  • And again:
    Daniel: Don't shoot! Just let them tend to Xe'ls.
    Jack: How do I know you're the real Daniel?
    Daniel: ...because.
    Jack: ... Yeah, okay. [lowers gun]
  • The second season episode "Holiday" also has a large dose of this. For example, when Jack and Teal'c have switched bodies:
    Hammond: How did it go, colonel?
    Teal'c (in O'Neill's body): It did not go well, General Hammond.
    O'Neill (in Teal'c's body): Ya think?
  • "Urgo" has a similar case as "Crystal Skull" above: Everyone in SG-1 has brain implants inserted in them on an alien planet which end up manifesting the titular Urgo, a person only they can see and hear. At the end of the episode they return to the planet and explain the situation to Togar who did this in the first place to get the implants removed. However, there is a problem: The implants will cease to function outside of a host brain, effectively killing Urgo, whose existence was an unintended side effect in the first place. The situation is solved when they convince Togar to take one of the implants himself. But with the implants removed, SG-1 can no longer see or hear Urgo, so how do they know he really survived?
    Daniel: Wait, Togar, how do we know that Urgo's really alive?
    Urgo: I'm here, I'm here, tell them, tell them!
    Togar: I will as soon as you are quiet!
    Daniel & Jack: He's alive.
• The ancient communication stones used in Stargate Universe seem to be setting up for a whole swath of this trope. The stones allow faster than light communication through the simple expedient of swapping bodies with the host receiver at the other end. It kicked off in episode 9 with one of the crew being allowed to visit her girlfriend/lover back on Earth, but doing so in the guise of a different body. Asked if it was really her, the [blue eyed, Anglo] stranger replied in fluent Cantonese "Have you thrown away that ugly red chair yet?", which satisfied her lover as to her identity.
• Star Trek: The Original Series
  • In "Turnabout Intruder", Kirk, while trapped in his ex-lover's body, tried to convince Spock that he was him. He mentioned certain events where Spock had helped him and urged him to help him again. Subverted when Spock calmly pointed out that those events could be easily read from the captain's logs and reports.
  • It's rather bizarrely subverted in "Whom Gods Destroy", where an insane former Starfleet officer develops the ability to morph into other people, and Spock is presented with two Kirks at the climax. He somehow can't come up with any questions that only Kirk would know, just so the episode can end with a fight scene. Leonard Nimoy himself was quite upset about it.
• In one of the most brutal subversions of this, in Star Trek: The Next Generation, the completely altered Jean-Luc Picard, aka Locutus, addresses the Enterprise crew after their failed attempt to destroy him. "Your resistance is hopeless... Number One." The look on Riker's face, and the crew's, was pure Oh Shit!!. The Reveal here is that Locutus - and therefore the Borg - had access to all Picard's memories, and therefore knew all the Federation's plans to try and defeat the Borg.
  • Played straight in the episode "Schizoid Man", where Picard is satisfied that Data has shaken off Ira Graves's attempt at Brain Uploading because Data has returned to his normal, slightly-too-precise philosophy.
• In Star Trek: Deep Space Nine, a hostile changeling takes on the form of Odo, knowing it's the one thing the Defiant crew can't test for. As the identical changelings face off, each one tries to tell O'Brien something that presumably only the real Odo would know. O'Brien subverts the trope by quickly putting a stop to the whole thing.
  O'Brien: I've got more important things to do than play "choose the changeling"! (To his assistant) Keep the phaser on both of them.
  • A lighter Deep Space Nine example comes in the episode "Children of Time", when an alternate-future Dax host suggests he could do this to prove that he really is Dax, and proceeds to recount one of Curzon's memories of Sisko...one that Sisko clearly doesn't care to remember.
    Yedrin Dax: Do you remember that dancer that you met on Pelios station? The one who...
    Sisko: (interrupting) The one who — that'll do. Thank you.
• Inverted by the CBBC series Stupid!. In one episode, King Stupid and his gremlin butler Goober plan to get rid of Stupid’s Evil Twin, Count Cruel by sending him to the real world. Unfortunately, Cruel overhears the plan, and dresses as Stupid. After a bit of back and forth between them, one of them then promises Goober a day off if he’s spared, causing Goober to fire the teleportation beam at him, as the real King Stupid would never give Goober a day off, even if his life depended on it.
• In Switched, there's a physical variant — as opposed to spoken dialogue — during the climax where the four teens confront each other. Umine's mother appears off-screen and yells her daughter's name. Ayumi-as-Umine responds to the yell, but Umine-as-Ayumi is immediately terrified and looks right at her mother, who then says "I didn't believe it until seeing your face."
• In Terminator: The Sarah Connor Chronicles, being a Terminator Spin-Off, "come with me if you want to live" is how Cameron identifies herself to John.
  • It also helps that he has seen her shot a minute ago.
• A storyline on Third Watch had the cops are searching for a pair of rapists who pose as police officers so that they can pull women over and then assault them. At the episodes end, as the fake cops are menacing a woman, the real cops arrive. The fake cops try to claim that the woman's screams for help are just the raving of someone high on drugs. Already suspicious (they know the woman and know she's not an addict), one of the real cops asks the fakers a question in "cop lingo". When he's unable to answer, they instantly know they've caught the criminals.
• An episode of Touched by an Angel had a local politician's longtime friend, a high school teacher, being accused of statutory rape. She believed his vehement denials due to their friendship and that she had overheard the girl vowing "to get back at him" for a poor grade. To that end, she obtained a copy of the girl's complaint... and was shocked to realize that the girl was telling the truth. How? She quoted, word for word, the same cheesy seduction lines that the man had used on her 20 years prior.
• The Twilight Zone (1985): In "Shatterday", Peter Jay Novins tests his alter ego's claim to be him by asking him what his childhood friend Skip Fisher's father did for a living. He correctly answers that he was a fireman until he quit his job to work at a Studebaker dealership.
• The main plot of the The West Wing episode "Shibboleth" was around whether the Bartlet Administration should grant asylum to a group of stowaway Chinese found in a ship container; they claimed to be Christians being persecuted by the Chinese government, but among the myriad array of political pressures from both Christian groups and the Chinese government (trade talks were on the horizon) there were also questions as to whether their professed faith was genuine as there had been previous instances of stowaways being coached into saying that. Bartlet has a one-on-one meeting with one of the refugees who can speak English and begins by asking him to list the Apostles; the refugee answers correctly but points out that being a Christian wasn't about memorizing historical figures but rather that "faith was the true shibboleth". Bartlet, himself a devout Catholic and who had previously used that same expression, determines from that response that they were truly Christians and arranges a way for them to remain in the United States by having the California National Guard, who was guarding them to this point, stand down and allow the refugees to escape custody — this would both let the refugees go free while also give the Chinese government a face-saving excuse to avoid jeopardizing the upcoming trade talks.
• Willow: Jade and Kit demand Boorman verify it's him as a result of the many magical hallucinations they've experienced in Nockmaar castle. Boorman shows that it's him by making a flippant comment revealing he knows they're attracted to each other.
• In an episode of Wings, Brian is caught in a bank robbery and hears the masked robber use the unusual phrase, "We'll all be sitting in butter!" Later, as he flies an unknown client back to the mainland, the client uses the same phrase, cluing Brian in to the fact that he's transporting the robber.
• In the Without a Trace episode "Suspect", the agents believe that the Victim of the Week has been abducted by the headmaster of his school. When one of them questions another student, the boy tells him, "He was going to invite him over to his house for a barbecue, then tell him that it was cancelled, then invite him to stay for a drink. . ." The agent instantly realizes that there's only one way that he could know that and gently asks him, "Did he do that to you?", which the kid confirms.
• Wizards of Waverly Place: When the Russos create duplicates of themselves to escape the government agent, Professor Crumbs recognizes the real Alex when she tells him that his beard stinks.
• The X-Files
  • In the critically acclaimed episode "Beyond the Sea", the psychic death row inmate (although whether his abilities are real or not is made deliberately ambiguous) freaks out Dana Scully a lot by referring to her by a nickname only her recently-deceased father calls her.
  • Also, in the two-part episode "Dreamland", in which Mulder switches bodies with an Area 51 worker. He tries to convince Scully that it's really him by rattling off some of her personal information. She is not impressed.
    Mulder (as Morris): I'm Mulder. I'm really Mulder. I switched bodies, places, identities with this man Morris Fletcher, the man that you think is Mulder, but he's not. Of course you don't believe me. Why was I expecting anything different? Your full name is Dana Katherine Scully. Your badge number is... Hell! I don't know your badge number. Your mother's name is Margaret. Your brother's name is Bill Jr. He's in the Navy and he hates me. Lately, for lunch, you've been having this six-ounce cup of yogurt, plain yogurt, into which you stir some bee pollen because you're on some kind of a bee pollen kick even though I tell you you're a scientist and you should know better.
    Scully: Look... Any of that information could have been gathered by anyone.
    Mulder (as Morris): Even that yogurt thing? That is so you. That is so Scully. Well, it's good to know you haven't changed. That's somewhat comforting.
• In the Young Blades episode "The Chameleon", after Captain Duval gets himself thrown in jail and the Musketeers believe he is a shapeshifter trying to frame Duval:
  Siroc: If you're the real Captain Duval, tell us something only he would know.
  Duval: Like what?
  D'Artagnan: Like what we got you for your last birthday.
  Duval: Nothing. Bunch of thoughtless, shiftless recruits.
  Siroc: Yeah, that's the Captain.