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[[quoteright:349:[[Manga/SeitokaiYakuindomo https://static.tvtropes.org/pmwiki/pub/images/mistakenage.png]]]]
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-> '''Godfree:''' Now now, Sir Kirito. Thou must respect thy elders. What he lacks in youthful good looks, he more than maketh up for with decades of experience!\\
'''Kuradeel:''' I'm...26.
-->--''WebVideo/SwordArtOnlineAbridged''


Characters assume another character's age, often based on common assumptions of traits that character has, or there can be other reasons.

A common one is an aunt (or uncle). In many cultures aunts are thought of as old, so when the aunt turns out to be only a few years older than the niece/nephew, it can be quite a surprise.

Commonly a consequence of having NeverGrewUp.

Compare VagueAge, ExpectingSomeoneTaller, ActuallyThatsMyAssistant, OlderThanTheyLook, YoungerThanTheyLook, ReallySevenHundredYearsOld, AgeInappropriateDress, and AssumingTheAudiencesAge.

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!!Examples:
[[foldercontrol]]

[[folder:Advertising]]
* The Grape Nuts cereal television ad: [[https://www.youtube.com/watch?v=3UnJSTpHsXc "Mrs. Burke, I thought you were Dale!"]]
** Later followed by the Palmolive "Which hands belong to the daughter?"
* One ''Oil of Olay'' commercial had a stage psychic guess a woman's age, and undershoot because she was using the product. She plays along, and says the psychic was correct.
[[/folder]]

[[folder:Anime and Manga]]
* It's a running gag in the ''Literature/{{Baccano}}'' light novels that, despite nearly half the cast being immortal, only Firo (already [[OlderThanTheyLook a bit young-looking]] before immortality) has to deal with the annoyances of not looking his age, such as getting carded at age ninety, being detained for claiming he was seventy on his passport, and constantly being called 'babyface'.
* In ''Anime/DenNohCoil'' Haraken's aunt, who is referred to offhand as being the commander of the Satchiis, is assumed by the main characters to be at the very least middle-aged. When she finally appears, it turns out that she's actually on the nearer side of twenty.
* This is actually the {{Berserk Button}} of Maria from ''Manga/HayateTheCombatButler''. She continually states that she's 'only 17' while everyone around her assumes she's older because of the aura she puts up, and being Nagi's {{Cool Big Sis}}/Mother figure.
* Hinata and Nishinoya in ''Manga/{{Haikyuu}}'' are often mistaken for younger than they are due to their height. In one instance, a volleyball referee even questions whether they're in middle- or elementary school. Both were in high school at the time with Nishinoya being a second-year. On the other hand, Asahi (a third-year in high school and 17 at the time) [[YoungerThanTheyLook looks older]] and is frequently mistaken for an adult who was held back several years.
* The protagonist of the first story in ''Himitsu Kichi'' mistakes a sixth grader for a college aged student. In turn he mistakes her for a kid his age when she's 16 years old.
* In ''Manga/LuckyStar'', Miyuki's mother looks so youthful and cute that she's actually often mistaken for her older sister rather than her mother.
* In ''Manga/MassuguNiIkou'', Mametarou mistakes Shokora for a puppy. Shokora is actually seven years old.
* ''Manhwa/TheMonstrousDukesAdoptedDaughter'': Characters frequently mistake twelve year-old Leslie for being about nine or ten, as she is smaller and skinnier than she should be for her age due to her abusive upbringing including not feeding her properly. This is exaggerated when she meets Bethrion. Between his only frame of reference being his younger brother and the fact that his family are all naturally large people, he initially assumes Leslie is ''five''.
* As shown in the page image, in ''Manga/SeitokaiYakuindomo'' Suzu Hagimura is frequently mistaken for a small child due to [[TheNapoleon her short stature]]. Naturally, this is a major BerserkButton for her. One of the most memetic moments in the series has a foreigner whom she helped give directions to mistakenly call her a "little girl", causing her to flip out and [[ClusterFBomb yell the F word]] as he walks away.
* In ''Manga/UzakiChanWantsToHangOut'', this happens when [[OlderThanTheyLook the 19-year-old Hana Uzaki]] meets her friend Shinichi Sakurai's boss for the first time. He initially assumes Hana's a middle school student, [[HeightAngst much to her indignation]], and disbelieves he misread her. A quick look down at her sizable chest does convince him she's an adult, though.
[[/folder]]

[[folder:Comic Books]]
* ''ComicBook/{{Batgirl}}'': A flashback had a then-teenage Batgirl meeting ComicBook/GreenArrow for the first time. He casually flirts with her and cradles her. Barbara begins laughing and says his cologne smells like her father, which causes a {{squick}}ed Oliver to back off. In hindsight Barbara says her costume [[YoungerThanTheyLook made her look at least twenty]].
* ''ComicBook/FantasticFour'': The Thing frequently mentioned his 'Aunt Petunia', with the implication that she was an old woman. When she finally appeared in the comic during Creator/JohnByrne's run, Petunia (she prefers 'Penny') was revealed to be his uncle's second wife and an attractive woman about the Thing's own age.
* ''ComicBook/{{Superman}}'': In ''ComicBook/ActionComics'' #865, the Toyman assumes that Jimmy Olsen is 17. Jimmy indignantly corrects Winslow Schott that he's actually 22.
[[/folder]]

[[folder:Fan Works]]
* In the ''Franchise/{{Splatoon}}'' fic ''Fanfic/HerFracturedSpirit'', Callie is older than Marie. Everyone thinks it's the other way around because Marie is so mature and aloof while Callie is so free-spirited and exuberant.
* In ''Fanfic/MyMasterEd'', Van Hohenheim is shocked when he finds out Edward is sixteen, having assumed he was closer to twelve. Edward's not doing any better upon finding out Van's fifteen, mostly because Van's already taller than him despite being the younger of them.
* In ''Fanfic/LoveWorthWaitingFor'', Mulan isn't able to figure out that Elsa is 23 by looking at her. Elsa looks [[OlderThanTheyLook younger]].
* In ''WebVideo/{{RWBY ABRG}}'', Weiss tells the teenaged Penny that she looks like a twelve year old.
* Mob in the ''Webcomic/MobPsycho100'' gender swap fanfic ''[[https://www.fanfiction.net/s/13226631/1/Shigeko-Kageyama-AKA-Mob Shigeko Kageyama AKA Mob]]'' because of the fact that as a female Mob carries herself more like an adult than most teenage girls, how quiet she is, and how she is always seen with Reigen, a grown man. Truth in fiction as females are often assumed to be older than they are once puberty hits.
* ''WesternAnimation/TheLoudHouse'' fanfiction:
** In ''Fanfic/TheNightmareHouse'', Lisa, a preschooler, has a nightmare involving being sent back to daycare and put in a diaper. A teddy bear thinks she's a baby.
** From ''Fanfic/TheBoyWhoCriedIdiot'':
*** Martin mistakes Chandler, a preteen boy, for a grown ''woman''.
*** Implied when Martin mistakes all the Loud sisters for Lincoln's kids; he must have thought that Lincoln's older sisters were younger than him.
* ''Fanfic/HardBeingPure'': Dr. Emilly is stuck at the appearance of a 10-year-old girl, and hates how she gets treated like a child even though she is mentally a 27-year-old.
* In ''[[https://archiveofourown.org/works/17401478/chapters/42427079 What You Knead,]]'' due to Kakashi’s gray hair and him having spent the last few years in semi-retirement, Sasuke and Sakura assume he’s at least middle-aged. When he tells Sakura he’s twenty-seven, she’s so embarrassed she practically runs out of the room.
[[/folder]]

[[folder:Films -- Animation]]
* In ''WesternAnimation/TurningRed'', Ming assumes that Devon is 30 when he's actually 17.
[[/folder]]

[[folder:Films -- Live-Action]]
* In ''Film/AnchorsAweigh'', two Navy sailors take a runaway kid back to his home, where he lives with his aunt. They think she must be old, and are surprised that she is about their age.
* ''Film/CaptainAmericaCivilWar'' introduced a YoungerAndHipper version of Aunt May than is traditionally depicted in the ''ComicBook/SpiderMan'' franchise. Her first scene involves some LeaningOnTheFourthWall where Tony Stark expresses surprise at how young she is, to which she responds that an aunt can be any age. Her age is perfectly plausible, since Creator/MarisaTomei was 51 at the time.
* Another younger than expected aunt in ''Film/AFewGoodMen''.
* In the ''Literature/TheBabySittersClub'' movie, the parent of one of Stacey's baby-sitting charges warns her in advance that her "little cousin" from abroad will be home when she comes by to baby-sit. She brings with her a little American flag to give him, expecting a young child. Instead, he's an extremely attractive 18 year old.
* In ''Film/IndianaJonesAndTheTempleOfDoom'', Willie Scott dresses up beautifully for the dinner at Pankot Palace in hopes to impress the wealthy Maharajah. She's chagrined when he's revealed to be a kid around the same age as Short Round.
* Used with SugaryMalice from the evil fiance in ''Film/TheParentTrap1998'' - where upon meeting Annie (disguised as Hallie), Meredith says she excepted a little girl as opposed to the "so grown up" eleven-year-old.
[[/folder]]

[[folder:Literature]]
* Early in ''[[Literature/AuntDimity Aunt Dimity: Detective]]'', Lilian Bunting asks Lori to entertain her nephew "Nicky" while she and her husband attend Prunella Hooper's inquest. Lori expects to receive a visit from a small boy, and is surprised when thirty-something Nicholas Fox introduces himself.
* In Creator/MaryRenault's ''The Last of the Wine'', the main character's lover has a spazz attack when he realizes that the woman the main character has been calling "Mom" for the whole book is a stepmother and about the older lover's age.
* ''Literature/DorothyMustDie'': Mombi is often referred to as an old witch. This is accurate-ish in the main series, but it's a severe case of [[YoungerThanTheyLook Younger Than They Look]] in ''Queen of Oz'', when she is referred to as an old witch despite being in her 30s-40s.
* In ''Literature/TailchasersSong'', Tailchaser is asked if he's 6 months old yet. He sheepishly mentions he's turning 9 months soon. In human terms, this is essentially equivalent to mistaking a 17 year old for a 12 year old.
* In the prequel ''Literature/TalesOfDunkAndEgg'' novella "The Sworn Sword", Dunk is sent to meet Lady Rohanne Webber, who he knows to be widowed multiple times (and rumored to have [[BlackWidow murdered her husbands]]) and who has a terrible reputation for cruelty. As a prank, Dunk is introduced to one of Lady Webber's attendants and is told that she is Lady Webber, and he believes it, because the elderly and [[{{gonk}} unpleasant looking]] woman jibes with his assumptions about what Lady Webber would look like. He then learns that a pretty young redheaded woman practicing archery nearby is Lady Webber, and that she is not nearly as bad as her reputation suggests.
* Used tragically in the first arc of ''Literature/WarriorCats''. The other Clans notice that the [=ShadowClan=] apprentices are abnormally small but chock it up to malnourishment. It turns out that Brokenstar is [[ChildSoldiers making three-to-five moon olds]] into apprentices. This turns out tragically when, during battle, a warrior attacks a three moon old named Badgerpaw and kills him.
* In ''Literature/PatienceAndSarah'', Sarah decides to move from Connecticut to York state by foot [[SweetPollyOliver disguised as a man]]. She's twenty-one but her lack of facial hair and boyish look makes everyone guess she's fourteen at oldest. This leads to trouble because she's routinely mistaken for a runaway apprentice.
[[/folder]]

[[folder:Live-Action TV]]
* ''Series/DoctorWho'': It's a RunningGag that the 12th Doctor (played by Creator/PeterCapaldi) constantly insists that Clara (played by Creator/JennaColeman) looks older than him, despite the fact that Capaldi is twice the age of Coleman, and as a Time Lord the Doctor is well over a ''hundred'' times older than Clara. A fan theory is that since Clara [[spoiler:jumped into the Doctor's timestream to save him from an enemy that was attacking him at every moment of his life]], the Doctor instinctively sees her as the same age as himself.
* In an episode of ''Series/{{ER}}'' an injured toddler comes in and shouts that Uncle Charlie hurt him. Someone asks if they should call Social Services only for someone else to point at another, unharmed but still grouchy, toddler, and say "That's Uncle Charlie".
* In an episode of ''Series/{{Firefly}}'', Mal invokes this trope to evade INeverSaidItWasPoison, when asked whether he has seen fugitives, "a brother and sister", by pretending to assume that the pair in question were children, when he actually knows exactly who and where they are.
* It's never explicitly stated what Niles expected in ''Series/{{Frasier}}'', but he is clearly surprised the first time he meets Daphne, mentioning that Frasier told him she was English and um, well... He most likely assumed she was a stuffy older lady.
-->'''Niles:''' ''You're'' Daphne?
* In ''Series/HannahMontana'', while making a video for their retiring principal, Lilly compliments him for not looking "a day over 80", which Oliver has to correct as he's ''only 65''. Lilly then tries to ammend her statement by saying it's because [[NotHelpingYourCase he reminded her of her dead grandfather]], who "didn't die of old age, [[DiggingYourselfDeeper he got hit by a school bus]]."
* [[Series/HouseMD House]] mistook a 37-year-old patient to be at least 10 years younger than she actually was, which turns out to be a clue for her illness. [[spoiler:She has "pretty leprosy", a form of leprosy that ended up making her look better, instead of making her skin fester and rot off.]]
* In episode 13 of ''Series/MimpiMetropolitan'', Prima and Alan are surprised when they find out that Bambang is born in 1998 just like them. Since Bambang always uses honorific for older person when referring to them, they assume Bambang is somewhat younger than them. Turns out that's just how Bambang speaks to most people.
* Charlie in ''Series/{{Numb3rs}}'' was once invited to a bed and breakfast in Santa Monica after publishing his first paper. Unfortunately, he was fourteen at the time and he had to break it off to a very embarrassed female professor in Berkley.
* In an episode of ''Series/UnitedStatesOfTara'', Kate's boyfriend is about to meet Kate's family, and Kate had previously mentioned that she had a younger brother. Kate's boyfriend buys a toy train, expecting that he'll be quite young, except Marshall (Kate's brother) is in his teens, causing an awkward interaction.
[[/folder]]

[[folder:Music]]
* Music/{{Hedley}}'s "Don't Talk To Strangers" is about a man who has sex with a woman. The morning after, he realizes that she's twice his age and old enough to be his mother. He literally went to school with her son.
[[/folder]]

[[folder:Professional Wrestling]]
* [[Wrestling/EddieGuerrero Eddie]] and [[Wrestling/ChavoGuerreroJr Chavo (Jr.) Guererro]] were close enough in age to be brothers (almost exactly 3 years apart), but they were [[WrestlingFamily uncle and nephew]].
* {{Wrestling/Paige}} had to remind fans that she turned 30 in 2022, in response to being treated as though she was still 19 as she had been when she first debuted in WWE (although 21 when she made it to the main roster).
[[/folder]]

[[folder:Radio]]
* ''Radio/OurMissBrooks'':
** In "Mr. Boynton's Parents", [[ExactlyWhatItSaysOnTheTin Mr. Boynton's Parents]] mistake a housecleaning Miss Brooks for old Mrs. Davis.
** In "Former Student Visits", Miss Brooks is desperate to appear young. She tries to hide the fact that she's already been teaching high school for several years. Unfortunately for her, the "former student" visiting had been in her very first class. He's since graduated from medical school and become a doctor!
[[/folder]]

[[folder:Theater]]
* ''Theater/TheImaginaryInvalid'': Diafoirus the younger is presented to Argan's daughter Angelique (which he's intended to marry) and gives her the speech intended for his future mother-in-law. Although it's meant to show Diafoirus as a dumbass, Argan's second wife Beline ''is'' a GoldDigger, so it's quite possible she's around the same age as her stepdaughter.
[[/folder]]

[[folder:Video Games]]
* In ''VideoGame/PokemonSunAndMoon'', when Hau first meets Lusamine, who runs the Aether Foundation, Hau assumes she is a TeenGenius and admires that she can achieve so much in such a short time. Lusamine then points out that she's actually well over 40 years old, and she [[OlderThanTheyLook only looks so young]] because [[ItMakesJustAsMuchSenseInContext she knows the right things to wear]].
* One of the races in ''VideoGame/FinalFantasyXIV'' is the Padjal, {{Horned Humanoid}}s gifted with eternal youth. During the Dark Knight story, Sidurgu mistakes E-Sumi-Yan for a boy, but the Conjurer corrects the "young man" that he is several times his age. Indeed, Brother E-Sumi-Yan, according to ''Encyclopedia Eorzea'' is over two hundred years old.
* ''VideoGame/GranblueFantasy'': In her 5★ Uncap, there are some Human children who naturally mistook Charlotta as a fellow child. The scene may also double as a RuleOfFunny moment due to the casual, yet playful manner of the children while talking to her. Perhaps they are not aware that they are talking to a Harvin (a dwarf race).
-->'''Charlotta''': Wha?! I-I may look this way, but I assure you I'm an adult!\\
'''Child ''': C'mon, lady! You ain't bigger than my little sis! And she just started talking last week!\\
'''Charlotta''': Grrr!
* ''VideoGame/LonelyWolfTreat'': Mochi is short and childish looking, despite actually being 19-20, so naturally she's mistaken for being younger than she actually is often.
* ''VideoGame/SakunaOfRiceAndRuin'': Sakuna is ReallySevenHundredYearsOld, but looks like a child, and she's irritated when pointed out in the beginning.
[[/folder]]

[[folder:Web Comics]]
* In ''Webcomic/TowerOfGod'' this happens commonly since the Shinsu atmosphere slows down and sometimes even stops aging. This leads to cases of Shibisu being in his late twenties and Yeon and Hatz in their late teens whereas Endorsi is about 300 years old and her "niece" Anaak is even older.
* A RunningGag in ''Webcomic/HannaIsNotABoysName,'' as one of the few things that seems to really aggravate [[ThePollyanna Hanna]] is when people mistake him for a teenager. ("'''''I'm 24.'''''") He certain [[OlderThanHeLooks looks young]], but it's never made clear if that has a [[AmbiguouslyHuman supernatural basis]] or if he's just naturally scrawny.
* ''Webcomic/BelovedL'' starts with the protagonist finding out she slept with a sixteen-year-old girl she met at a bar.
* In ''Webcomic/TrueVillains'', Sebastian assumes that the LadyOfBlackMagic Elia is in her mid-twenties like him, and is flabbergasted to hear that she's actually in her eighties -- a perk of being a {{Necromancer}} who can [[FaceStealer steal a young woman's skin]] whenever she wants to restore her youth. It doesn't diminish his interest in her.
* In ''Webcomic/ElGoonishShive'', Amanda exploits [[https://www.egscomics.com/egsnp/2004-08-31 having drunk a soda]] with a FountainOfYouth formula by [[https://www.egscomics.com/sketchbook/2004-09-05 going up to an age guessing booth.]]
* In ''Webcomic/OnePunchMan'', Saitama doesn't initially believe that the [[PersonOfMassDestruction S-Class Hero]] Tatsumaki is in her 20's, instead mistaking her for a random BrattyHalfPint that somehow got into the Hero's Association building.
-->'''Saitama:''' What's with this sassy...lost child?
[[/folder]]

[[folder:Web Video]]
* WebVideo/ContraPoints once {{Squee}}d about a taxi driver asking her about college, liking that she was still seen as young enough to be a student. She was in her mid-30s when the video was uploaded.
[[/folder]]

[[folder:Western Animation]]
* In ''WesternAnimation/AlvinAndTheChipmunks'', Alvin hears about having an oldest fan, and thinks she's just in her twenties, while she is actually a senior citizen.
* Comes up in an episode of ''WesternAnimation/FamilyGuy'', where Quagmire (who else?) meets a girl at Peter's party and sleeps with her, thinking she is 18, only to find out that she is 16. (Granted that ''is'' still the age of consent in Rhode Island, [[RuleOfFunny but who cares?]])
* One episode of ''WesternAnimation/TheLoudHouse'' has Stella offend [[SternTeacher Mr. Bolhofner]] by thinking he's 62. ''He's 34!''
* In the ''WesternAnimation/StevenUniverse'' episode appropriately titled "Steven's Birthday", 12-year-old Connie (and the audience) is shocked to learn that Steven is turning 14, having assumed that he's at least a year younger than her due to his short stature and childish behavior. The characters wonder if Steven's HalfHumanHybrid nature has affected his natural growth, as he has looked essentially the same since he was eight, then speculate if he will age any more than he already has.
[[/folder]]
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