Katelynn Zales: [naked] I'm a turkey!
Mackenzie Zales: God dammit, Katelynn! I'm sorry, Deandra.
Deandra: Oh no, no problem. This girl actually reminds me a lot of myself when I was two.
Mackenzie: ...She's seven.
You turn on the TV and start watching it. Apparently, some child actor is guest starring. But wait a minute. How old is his character? He says he's X, but he's acting like X minus 5. What kind of 14-year-old gets real excited over a balloon? 10-year-olds don't (usually) watch Nick Jr.! Wait, a 12-year-old still believes in the Tooth Fairy? Why is a 15-year-old still playing with toys? To put it simply, that character is a Kiddie Kid.
Basically what happens when Most Writers Are Adults is applied, but instead of the writers writing about issues relevant to them, they try to guess what kids act like and hit below the target age. On other occasions, writers may have a kid of the appropriate age in mind, but the director winds up casting a child in the role who's much older than intended (this is especially prone to happening in adaptations). This may also happen when a show featuring teenagers is being marketed to younger kids, so they make the teenagers act like the target audience.
Television Without Pity was biting about this in a recap: "Scriptwriters who have no experience with real children tend to write them as perpetual babies" and then gave an imagined scene from the then-current season of Judging Amy where the main character becomes furious that her daughter knows what the word "sex" is, as if her daughter is a kindergartener, even though the daughter (and the daughter's actress) was entering adolescence when the TWP recap was published.
In more justified cases, the kid in question has not had a conventional upbringing (e.g. they're orphans, homeschooled), causing them to have a naïve outlook. They may also act younger than their age due to being neurodivergent. Values Dissonance may also play a part: in Japan, for example, childishness is considered cute (at least in girls).
Can be a side-effect of Competence Zone. Contrast Wise Beyond Their Years and Acting Your Intellectual Age. Related to Menace Decay. When it's an adult behaving younger than their stated age, it's Manchild and/or One of the Kids.
This can be Truth in Television for some, since not everyone acts as mature as or shares the same interests as others.
- One Dora the Explorer commercial had an elementary-school-aged girl who was obsessed with and kept talking about the show, which was supposed to be for preschoolers.
- Case Closed: Conan, as a high-schooler trapped in a child's body, also acts rather immature from time to time, to the point where his child-age friends call him out on it.
- Code Geass: Subverted with Nunnally. She's introduced at age fourteen but her design, voice, and Ingenue personality all suggest she's younger. Her older brother Lelouch also coddles her in part because she's blind and partially paralyzed. During the second season, which takes place a year later, Nunnally's more mature side becomes more apparent.
- Lampshaded in Cute High Earth Defense Club LOVE! with Yumoto. He is 15, but generally acts much younger than that. When one Monster of the Week turns him and his friends (who do act more like actual teenagers) into elementary school children, the other boys point out that Yumoto didn't change at all.
- Son Goku from Dragon Ball looks like an 8-year-old well into his mid-teens and has the wisdom of a child even younger than that. For the record he never quite grows out of this and becomes a Manchild when he reaches adulthood.
- Lampshaded in regards to Arale from Dr. Slump. Her creator intended her to be 13, but several characters have pointed out that she doesn't look or act like a teenager.
- Zigzagged with Wendy (12 years old) in Fairy Tail. She is quite intelligent and regularly acts just as mature/like an Only Sane Man to the other protagonists, who are 5-7 years older than her. But she seems to have a love for stuffed animals and toys that most 12-year-olds have outgrown. She has a rabbit backpack, has her room filled with teddy bears, and in one of the OVA's, she eagerly carries around a doll and wails like an infant when it is destroyed. She also sometimes shows Cheerful Child traits.
- Gintama: Kagura zigzags this trope. She is fourteen, but how mature she is seem to vary depending on the situation. She is usually very childish, often hanging around with the neighbourhood children and playing games like bug catching and beetle fights with them, and early in the the show she seemed to be extremely naïve and gullible (though, that one might be because she just arrived on earth and didn't know anything about the planet), but other times she act her age, and is seen hanging out with other girls the same age. And then there are those times when things get really serious and she can act surprisingly focused, determined and level-headed for a 14-year-old.
- Midori Asakusa from Keep Your Hands Off Eizouken! often displays shades of this when caught up in her various fantasies, typically getting so deep into them that she starts acting them out with various items and architectural elements in a given environment like a little kid, even though she's in her first year of high school. Among other such moments, she dons a rusted bucket and pretends it's a space helmet while repairing the Motion Picture Club's dilapidated building, which she visualizes as herself mending a broken spaceship. She even wears light-up sneakers, which Tsubame lampshades as being more for kids.
- Nana and Narumi from Kimikiss Pure Rouge are 16, but they look and act half their age. In one episode, they are shown to care about romantic love by having their ubiquitous plush frogs marry.
- The main characters in K-On! are all high school girls (and they even graduate by the series' end, then go to college in a spin-off), and yet act more like 8 or 11-year-olds than most middle schoolers, yet alone high schoolers. Even Mio, the supposedly "mature" one, acts more like a very-slightly-more mature 12-year-old than anything.
- Most girls in Lucky Star are in their late teens, but the Puni Plush art style makes them look younger and they often talk about things that grade school kids would more likely talk about (such as how to eat certain foods or what kinds of animals they'd be). Tsukasa is innocent, keeps a whole bunch of stuffed animals in her room, and mentions wearing character-print underwear. Konata and Yutaka are Older Than They Look even In-Universe, and Yutaka thinks like an eight-year-old (her very first line is "Upsy-daisy"). And then there's Misao and her antics, such as making "pocky" by filling a straw halfway with chocolate milk.
- Aoko from Magic Kaito is 16-17, but is noted to act like a little girl sometimes and her speech patterns are quite child-like. It seems to come from her lack of self-esteem, however.
- The titular character from Naruto is a strange case. In Part 1, he is just a little bit immature, but not enough to qualify for Kiddie Kid. Thing is, all of his peers are affected by Most Writers Are Adults, so the difference in maturity by his peers qualifies him for this trope. In Part 2, he grows up and acts his age, though. The in-universe explanation is that he's acting out for attention, which may explain his lack of maturity.
- Himawari from Boruto is implied to be ten, but acts and is treated more like a six-to-eight-year-old.
- One Piece:
- Tony Chopper may count. He's 15, and only a couple years younger than Luffy, but he can also be very cowardly and is extremely gullible. Some people on the crew, like Zoro, defend him like a child caught in a battlefield when the situation calls for it. Slightly averted by the fact he really is competent on the battlefield, but his younger instincts get in the way. Part of it might have to do with that he was 8 years old when he ate the Human-Human fruit granting him his human-like capabilities.
- Usopp counts as well, he's 17 but hangs out with a group of 8-year-olds and plays with them all the time.
- Luffy himself is 17, now 19, years old and he certainly doesn't act like a teenager that age. He has the curiosity, love of adventures and new experiences, simple-minded logic, naivety and Brutal Honesty typical of a much younger child. Only in very rare situations when he gets pissed off or serious enough, he may show some leadership skills and actually act more mature than your average teenager. His childishness is complimented by how he looks like he has barely reached puberty yet.
- Carrot is one as well. She is at least a teenager, but act very curious, cheerful and energetic, and is naïve to the point that the aforementioned Chopper is the one acting like a Cool Big Bro to her. Justified by the fact that Carrot has zero knowledge of the world outside of her birth country of Zou, so she marvels at everything she discovers like a child, and seems quite gullible.
- Rebecca Miyamoto from Pani Poni Dash! is a Child Prodigy an MIT graduate and high school teacher at age ten, but often behaves in ways that remind the viewer that she's still very much a child. However, the way she behaves at times only make her seem much younger than even eleven, as she does things like throw tantrums, hide behind things and cry when frightened, address people by made up nicknames, or scream at the top of her lungs under stress.
- Azusa Shiratori from Ranma 1/2 is sixteen years old but acts like a two-year-old toddler most of the time, she throws violent tantrums, even bawls and screams like the big crybaby she is over some headphones Mikado wouldn't let her have.
- Sailor Moon: At fourteen Usagi is a carefree crybaby who loves childish things, just wants to have fun and can't keep up with the kind of schoolwork expected of her age. She eventually grows out of it over the course of the manga. Except for writing kanji, which is a Running Gag that continues even after she becomes Neo Queen Serenity, and other guardians treat it as a sign of Usagi still being a child at heart.
- Played for drama with Yuki from School-Live!, who is a high schooler but seems far younger. She wears a kitty-themed hat, has a backpack with angel wings on it, and is an All-Loving Hero. This is also reflected with her pink hair. Yuki acts so young that she's a Replacement Goldfish for Rii's sister, who is a grade schooler. Of course, this may just be one way she avoids the trauma of accepting that she's living in a zombie-infested hellhole. This trope is also deconstructed as prior to the story Yuki had no friends because the other girls thought she was weird.
- Yaya Yuiki from Shugo Chara! is around 10-11, but she often acts like a Bratty Half-Pint. However, this is actually Justified in the story itself— this behavior comes from her Infant Sibling Jealousy towards her younger brother. She desires to be loved and coddled by the people around her, so she acts like a big baby to get attention.
- Time Stranger Kyoko reveals Ui to be this upon her awakening. Justified, as Ui has been in suspended animation for years, and she has never gained the chance to mature. She's like a young child in an older teenager's body, who goes about her heart's desire like any child would.
- Rebecca Hopkins from Yu-Gi-Oh! seems like she's playing this trope straight at first. She's twelve, yet she's still carrying a teddy bear around, talks to it and uses it to talk for her, dresses childishly, and looks like she's about to throw a temper tantrum when Yugi get's the upper hand in their duel. However, it's quickly revealed that all this is an act to throw off her opponents. In her next appearance a couple seasons later, she dropped the little kid act and started acting her age. For the most part anyway.
- This is intentionally done with Jughead from Archie Comics. He's rather immature for a teenager his age. He even mentioned in the 40s radio show that he was fond of Howdy Doody, which was aimed at kids almost ten years his junior. His immaturity was originally shown off by his hat - in the early 20th century young boys would often cut up their father's old fedoras - however the fact has been lost by audiences over the years. Many think it's similar to a Burger King crown though, which has a similar effect.
- Foxtrot: Jason (a 10-year-old TV Genius) is terrified of girls getting mushy with him, sometimes even dropping the term "cooties" as though it were an accepted scientific phenomenon. Occasionally lampshaded by his usual target and Sitcom Arch-Nemesis Eileen whenever he's planning a stupid prank worthy of Calvin. He has gotten a little better in this regard over the years.
Eileen: Um, Jason, are you in the fifth grade because you skipped a few years?
- Molly from Runaways acts younger than her true age, intentionally, because it gets her attention and makes her feel loved. Plus, it gets adults to underestimate her. Which is useful, because if the emphasis is on the "cute" in Cute Bruiser, then people aren't expecting it when the cute little girl tosses them across the block (just ask Wolverine). This did lead to a brief storyline in one run where she wonders if she's doomed herself to always be seen as this by the rest of the group, however, and contemplates whether she should take a friend's Fountain of Youth offer.
- A downplayed version in For Better or for Worse since the characters are toddlers, but 2-3 year old Leah and Richard are treated more like infants. They still drink from bottles despite kids that age drinking from sippy cups, and Richard still eats mushed up food and speaks in simple babble such as "Ya-Gah" despite kids that age eating the same food as adults and speaking at least 2-3 word sentences.
- Played for Drama in Infinity Train: Blossoming Trail: Hop is usually depicted as a pre-teen who is capable of handling himself and is off on his own adventure to be a great Trainer. However, by the time we cut back to him when he's been stuck in The Fog Car (aka Silent Hill), he's somehow mentally regressed to a six or seven-year-old boy, acting affectionate and childlike to Alex Shepherd to the point he's asking for bedtime stories and drinking chocolate milk and butter cake before bed. This is presumably due to what Walter and Henry wish to enact for a ritual, needing seven people to embody certain aspects and Hop represents "Delight".
- In Alice's Adventures in Wonderland, Alice is 7 years old, so her personality makes sense. Most adaptations, including Disney's Alice in Wonderland, age lift her to 10-12, so in these versions her personality comes off as slightly immature for her age. It makes more sense for a 7-year-old to be utterly bored by books without "pictures or conversations," or to cry a big pool of tears when she finds herself grown into a giant. The fact that most of these film adaptations then cast a girl who is more in the range of 14-16 makes matters even worse still.
- Monsters, Inc.: Zigzagged with Boo, who is implied to be about two since she's potty trained but clearly still a toddler. Her vocabulary is more like an eighteen-month-old consisting mosting of babbling, but her drawing skills are rather advanced for a two-year-old.
- Done intentionally with Peter from Peter Pan. He has a Vague Age but seems to be nearing adolescence. However, he acts like a much younger boy than his Younger Than They Look appearance suggests. He doesn't want to grow up and avoids maturing at all costs. In the book, it describes him as a boy who has not yet lost his first baby tooth, which would reasonably put his age at about 6 or 7 at most.
- In Turning Red, this is downplayed. While Mei is your typical junior high girl who is experiencing the awkward emotions of puberty, crushes on older guys, idolizes a Boy Band with K-pop and Western influences, and often separates herself from her family in favor of her friends, part of her is still a little girl, as she carries around a Tamagotchi and decorates her room with stuffed animals, one of which in particular, Wilfred, is her Security Blanket which she still sleeps with.
- Robin in Batman Forever. The part was written for someone much younger than Chris O'Donnell, leading to jarring moments, such as Alfred convincing an obvious twenty-something to stay with Batman / Bruce Wayne by bribing him with a cheeseburger.
- Child's Play (2019) aged Andy Barclay up to 13 (from 6 in the original film). It's hard to imagine a 13-year-old boy being excited over a doll like Chucky, never mind that it's creepy-looking as hell even before it goes homicidal.
- In Down in the Delta, the autistic toddler Tracy still sleeps in a crib, even though it's noted that she's too old for it.
- Fred: The Movie ages the titular 6-year-old Cloudcuckoolander to a teenager, but he acts the exact same as in the web series.
- In Jack, Robin Williams plays a 10-year-old kid with a disorder that makes him age at 4x the rate. He, however acts like he's five, in part because he was sheltered and homeschooled until fifth grade.
- Jurassic World: Gray's character was supposedly written as autistic at first. While this wasn't specifically mentioned in the final film, it explains his Calvin-levels of excitement at seeing dinosaurs.
- Played tragically in Logan. Eleven-year-old Laura acts more like a child several years her junior due to her poor upbringing. In one scene, she begins to eat mashed potatoes with her hands, and even when she's given a fork, she doesn't know how to hold it correctly.
- In The Major and the Minor, Ginger Rogers must pretend to be 12, which she does by acting like she's 6.
- Possibly why Denny from The Room acts so weird—he appears to be in his late teens or very early twenties, and was played by a 26-year-old, but acts like a (strange) little kid who's just on the cusp of puberty and doesn't quite know how to handle it.
- In SHAZAM! and SHAZAM! Fury of the Gods, teen Billy as his own self is quite mature. When he is his Shazam self though, he acts and talks in a much less mature manner.
- In The Film of the Book Tom's Midnight Garden, Tom becomes this. While the book doesn't specify any age, it's pretty clear that he's a little boy. However, in the film, he is very obviously a young teen, and the actor who plays him, Anthony Way, is fourteen at the time of filming. Consequently, Tom's games in the garden with Hatty, while age-appropriate for the little boy depicted in the book, come across as rather childish for the young teenager we see in the movie.
- Susie in Too Much: The Robot With a Heart appears to be around 10 or 11, but acts very immature and childish for her age. The main plot is kicked off by her running away from home to be with her robot, who is now her best friend.
- An Agatha Christie short story uses this as a plot point: a teenager who gets really excited about showing a magic trick involving hiding a diamond to win a bet ends up really losing the diamond. It turns out she's part of a gang of jewel thieves, using her Older Than She Looks appearance to appear truly innocent. The detective who solves the case sums it up by saying "Children aren't that childish."
- Holden from The Catcher in the Rye is a mild example. He's seventeen but even he admits that he often acts as mature as a twelve-year-old.
- In the Confessions of Georgia Nicolson series, Georgia's younger sister Libby could qualify as this as she does not age along with Georgia, though she should be about six by the end of the series. She still isn't toilet-trained, speaks only in toddler-gibberish, still uses a pushchair, and her social skills only extend to shouting embarrassing things at passersby and cheerfully torturing her male "fwends" at nursery school with make-up and garden implements.
- In the Diary of a Wimpy Kid books, Greg's friend Rowley is one — although he's in early-middle school, he prefers to hang out with six-to-eight-year-olds, be it holding a birthday party at the local Suck E. Cheese's or having several kids from karate class for a sleepover.
- Eleanor & Park:
- Eleanor’s brother Ben is eleven (later twelve) and still plays with toy cars and doesn’t seem to hang out with the other boys his age. Eleanor actually hopes that he’s a late bloomer, as there’s no room for two of them to be teenagers in their Dysfunctional Family.
- Her other brother, two-year-old Little Richie, seems to act more like a baby. He never speaks and still rocked and carried around by their sister Maisie.
- Subverted in the Harry Potter books. In the earlier books, Ginny Weasley was only one year younger than the Trio, but was treated and described as though she were several years younger. In later books, it's made clear that she had always had a stronger personality and was more shy due to both her childlike crush on Harry and being the Weasley family's only daughter among several boys, so she starts acting more outspoken as time passes. You can debate all day whether this was a Retcon or planned all along, but either way the subversion is there.
- The Institute: Avery Dixon, one of the gifted kids taken by The Institute. He is ten, but he both looks and acts at least several years below that age (in his first scene he throws a tantrum like a toddler). Lampshaded by the other kids, with Kalisha theorizing that it's because Avery is a very powerful telepath, meaning he could live a pretty sheltered life and never had to learn social skills needed to pick up cues (like judging what people say by their expression and tone of voice).
- In the first half of Little Women, 13-year-old Beth generally acts like a younger child, especially in the way she still plays with dolls and treats them as if they were alive. All four of the March sisters are innocent for their ages, since their parents believe in letting children be children as long as possible, but it especially stands out with Beth.
- in the Ramona Quimby series, Ramona herself tends to behave as someone her age should, as is also the case for her sister Beezus and best friend Howie. Such is not the case, however, with Howie’s little sister Willa Jean. In the first book, Ramona is four years old and Willa Jean is around two, able to walk and say a few words. By the last book, Ramona is in the fourth grade while Willa Jean is around four or five, able to speak better but still “messy” and too young for school, with a toddler’s tantrums, etc.
- In Toms Midnight Garden, Hatty is one of these at one point. When she falls out of a tree, her aunt remarks that she shouldn't even be climbing trees at her age. Justified as Hatty is socially isolated, being ignored (at best) by her relatives, with her only friend being a time-traveling little boy.
- Wicked: Fiyero's nine-year-old daughter Nor still sucks her thumb, has a lisp where r's are pronounced like w's, and generally acts younger than she is. In Nor's case, it's just her as other kids don't act this way; it's implied Nor is spoiled.
- In Wuthering Heights, Edgar and Isabella Linton are introduced fighting over who gets to hold the family lapdog like a pair of 5-year-olds, Edgar crying and Isabella throwing a shrieking tantrum. Edgar is 15 in this scene and Isabella is 11. Of course, this was presumably an intentional choice to show the weak, spoiled nature of the Linton family. Also, it's only described secondhand by Heathcliff, who despises the Lintons and might be an Unreliable Narrator.
- When they're not interested in romance, the Big Time Rush band can be rather goofy. In one episode, Kendall tries to tell his mother that the guys are mature...while Logan and James are playing with chicken nuggets shaped like dinosaurs in the background.
- Cindy from The Brady Bunch, much to the annoyance of her actress Susan Olsen. The final season episode "The Snooperstar" had her obsessed with becoming the next Shirley Temple and singing "On the Good Ship Lollypop," despite being 12 years old. It was later revealed that this episode was originally planned for much earlier in the show's run, but Executive Meddling kept it until the last season, when it no longer made sense.
- Most early Long Runner TV shows where a kid main character's actor outgrew the original premise, most infamously the 1950s TV series based on Dennis the Menace (US); contemporary Leave It to Beaver was another case. Writers and showrunners accustomed to radio (where, as in animation, children were often voiced by adult women) had a learning curve to deal with.
- Get Smart: In one episode, a weapon is meant to regress people's minds into the mind of an eight-year-old, yet when the Chief is hit with it, he takes a nap. Eight-year-olds don't usually take naps unless they're sick or sleep-deprived.
- Doctor Who had characters like this in the early years:
- Susan in Doctor Who suffered from this in some stories, such as getting far too excited about going paddling in the sea and getting a new dress in "The Keys of Marinus" and her general childish reactions in "The Daleks" (displaying disproportionate screaming, rolling-around-on-the-ground terror when the Daleks allow her to return to the TARDIS through a spooky-looking nuclear wasteland containing no living things and confirmed to be safe, and giggling uncontrollably at the Daleks' funny voices). Part of the reason her actress Carol Ann Ford left the role so early was because she was frustrated with her character being written this way, although it can be Justified by the fact that Susan isn't human, and is from a species that is considered a kid until they're hundreds. Her replacement companion, Vicki was written convincingly like a clever fourteen-year-old.
- This was sometimes done intentionally in serials aimed at younger audiences in order to allow older characters to serve as Audience Surrogate characters. For instance, Steven (in his early 20s) and Dodo (a teenager) both act quite childish in "The Celestial Toymaker", doing things like laughing at clowns making the other jump, and getting cross with a creepy schoolboy character for cheating, being rude and not sharing sweets. It's a sharp contrast to their behaviour in "The Ark" and "The Savages", science fiction stories aimed at older children and teenagers, where they act their ages.
- In the Emergency! episode "Alley Cat," the firemen rescue a girl from a plane crash who looks about twelve, but acts closer to four. She calls her parents Mommy and Daddy, refers to her injured, unconscious father as "asleep in the plane," does an impression of a lion, and even calls her mother's bandages a "funny hat" and asks if she can have one. The adults around her act accordingly, with lines like "Why don't you one, two, three, four drink your milk?" The children of Emergency! usually act at least somewhat like their age, so her behavior is jarring.
- Played with in Good Luck Charlie with P.J. as a fan The Gurgles, a singing group for toddlers and TV show of the same name.
- Ben from Friends, Ross' son from a prior marriage. The more he showed up in later seasons the more "the same age" he remained, even though the actor playing him was obviously getting close to being 12, rather than being young enough to actually believe in Santa Claus, for example. He was all but forgotten after Emma was born, and only received mentions in passing.
- Scott from Hip Hop Harry—the actor portraying him is a teenager, but he acts very childish; he doesn't know how to cross the street by himself, he doesn't know what a lot of things are, and he thinks it's a good idea to feed hot dogs and ice cream to a hamster.
- Sometimes, when children's shows want to portray Audience Surrogates who can do more complicated things than their target audience can, like perform intense choreography or explain what it's like to live with a disability, they'll bring in an older kid who tends to fill this role. While Sesame Street and Barney & Friends have each done this a couple of times, Kiddie Kid moments happen fairly frequently on Hip Hop Harry, because the child actors on that show are hip-hop dancers who are all at least nine years old, and they're playing to preschoolers.
- Boyd from Last Man Standing. One episode lampshades it, in which he, as a 9-year-old, asks an adult to put holes in a box so his stuffed animals can breathe. Another episode has him, at age 10—meaning, a 4th or 5th grader—, shrieking in fear and running away from cheesy Halloween decorations in a school-run Haunted House, and later whimpering about facing the "scary monsters" like he's in pre-school.
- Dewey from Malcolm in the Middle starts off the series as a 1st grader (making him 6 to 7 years old) however in several episodes he behaves like someone way younger than his age. For example, throwing a tantrum when his parents won't buy him a "Sleepytime Herbie" doll.
- The Midnight Caller episode "Do You Believe in Miracles?" has a thirteen-year-old girl who spouts adorable one-liners like "Maybe he was grumpy because his hair hurt. It looked really sharp!" Surprising, since other episodes have kids her age who act more realistically adolescent.
- Screech from Saved by the Bell. He is the character with the least character developmentnote , and the goofiest to boot. It doesn't help that his actor is a few years younger than his costars, yet his character is the same age on the show.
- Smallville: In one episode, Lana Lang is haunted by the ghost of a childhood friend, Emily. Emily was stated to be 10 years old, but she looks and acts much younger, with handwriting that looks more like a 2nd grader and interests and speech patterns more typical of a 4- or 5-year-old. In flashbacks, Lana appears to have been an improbably immature 10-year-old as well, since she didn't act very differently from Emily.
- In the Star Trek: The Next Generation episode "Rascals", Picard, Ro, Keiko, and Guinan are de-aged into twelve-year-olds. They have the mentalities of adults, but when they (with the exception of Keiko, who never tries to act like a kid) try to act like children, they behave more like six-year-olds than twelve-year-olds. Picard, in an attempt to persuade a Ferengi to let him see Riker, stamps his foot and shouts, "Now!" over and over for instance, and Ro and Guinan jump on a bed.
- Played for Drama in The Twilight Zone (2019) episode "The Wunderkind," in which Oliver Foley, an eleven-year-old YouTube star, becomes President of the United States thanks to a savvy campaign manager. His first official act as president is to demand that everyone get free video games; he throws wild temper tantrums; and he refuses to get a female dog because Girls Have Cooties. It's somewhat justified in that Oliver is a Spoiled Brat with Extreme Doormat parents who coddle him endlessly and grant his every whim, so he feels no need to mature—and it's made worse when he fills his cabinet with sycophants who bend over backwards to indulge him. Oliver's extreme immaturity ends up killing his campaign manager, as his fear of doctors makes him enact a law which states that only children can be surgeons, leading to a bored ten-year-old slicing the manager to bits on the operating table.
- Cat Valentine from Victorious. Despite being a teenager in performing arts high school, Cat's demeanor is pretty much like a child with her baby voice, extreme naivety, and impulsive nature. Some of her most immature moments involve swallowing keys that were given to her and wanting to lick red lasers because she was curious about the flavor.
- "I Saw Mommy Kissing Santa Claus" was originally sung by a thirteen-year-old. The song, however, is clearly supposed to be sung by a far younger child. The wording and even the premise are too immature for most tweens.
- In the original story of The Nutcracker, Marie is seven years old. But in most productions of the ballet, Clara is cast with an eleven- or twelve-year-old dancer, or even with an adult ballerina playing her as about twelve, since the role's dancing demands are typically too much for a younger child. This means the audience needs to suspend their disbelief that a nearly teenaged girl should be so enamored of a simple nutcracker doll.
- In Ensemble Stars!, Tori looks and acts much younger than he is, but at least that's part of a deliberately cutesy act for him. Mitsuru, on the other hand, just naturally acts more like a primary schooler than the 15-to-16-year-old he is in canon. It says something when he sees Tomoya and Hajime as an older brother and sister when even they come across as younger than they really should.
- Fire Emblem:
- In the original Fire Emblem: Shadow Dragon & the Blade of Light and Mystery of the Emblem, Marth is rather naive and acts decidedly childishly, despite being 16 in the former and 19 in the latter. This was changed in the first game's remake, in which he acted Wise Beyond His Years, before the third game's remake reverted to his original personality, albeit somewhat toned down.
- In the Japanese version of Fire Emblem: Awakening, Nowi the Manakete, who looks about 11 or 12, acts like she's about 9 or younger, complete with Third-Person Person dialogue, in contrast with her daughter Nah who looks like she is barely 8 and acts at least twice that. The English version changes this somewhat, where she has Hidden Depths and is more mature than she lets on.
- From the same game, Chrom's little sister Lissa is 16, still afraid of a multitude of things, talks and acts childishly, has a high-pitched voice, and is a prankster. Depending on which ages the official profiles are using, she can be 18 post-Time Skip.
- In Heavy Rain, Jason and to a lesser extent, Shaun, are incredibly stupid for their age. Near the beginning of the game, Jason, age 10, is alone with Ethan in the mall. Ethan immediately tells him not to wander off, only for him to ignore his father, wander around in a jam-packed mall, and leave the place to watch TV at a nearby store. When Ethan finally sees him across the street, Jason runs without looking for cars and gets hit and killed. Two years later, when Shaun is the same age, one level is basically Ethan taking care of Shaun on a typical school afternoon. This includes Ethan making him a snack when at his age he could just look for something himself, sending him to bed at 8PM at the age where boys go to sleep between 9PM-10PM, and Shaun asking for his precious teddy bear. Shaun's case is a little Truth in Television since he comes from a broken family and coping with his brother's death, Shaun could complain to his mom and Ethan would lose custody if he didn't give as much care as Shaun expected, but he isn't completely excused. Apparently in earlier versions of the game's production, Jason was going to be 4 or 5 instead of 10, which would've made his behavior more understandable, but Sony felt that the death of a child that young would've been too tragic for players. He was aged up but his behavior wasn't corrected to match.
- In Honkai Impact 3rd, the twins Rozaliya and Liliya Olenyeva are officially between 12 and 14 years old, but their favourite pasttime, at least in the Dorm mode, is hide-and-seek. In one such interaction, Rozaliya guilt-trips their slightly older, and far more mature, fellow orphan Bronya (who'd rather play video games) into playing hide-and-seek with her.
- The Idolmaster
- Main Branch: At age 14 Iori carries a stuffed bunny wherever she goes, although said bunny makes less appearances in the 2nd Vision games after she turns 15, Yayoi is very innocent and acts more like a grade schooler than a 13/14-year-old, at the age of 12 Ami and Mami thought that receiving a reply from a letter to Santa is definitive proof of his existence, 16-year-old Yukiho still believes in Santa and 15-year-old Chihaya is also implied to as well, and 17-(later 18)-year-old Takane enjoys shows intended for preschoolers, although this is treated as unusual.
- Cinderella Girls: Chika Yokoyama genuinely believes Usako, Arisu's puppet, is really alive and talking. Chika is 9.
- SideM: Pierre is 15 but much like Yayoi is incredibly innocent and naive for his age. Kanon acts excessively cutesy for a 9-year-old boy and like Iori is often seen with a stuffed bunny, but this may just be because he's In Touch with His Feminine Side.
- Trails Series:
- Tita Russell from The Legend of Heroes: Trails in the Sky, not so much for her behavior (though she still has her moments of immaturity), but rather, the way the other characters treat her. She's 12, and a Gadgeteer Genius prodigy at that, but all of the characters talk to her in an almost condescending way like they would a much younger child, including Estelle and Joshua, who are only four years older than her! This forms a substantial part of her Character Development, as being treated like a kid frustrates her to no end, and she takes on increasing responsibility and danger to prove to the competent adults that she can pull her own weight with the best of them.
- Similarly, Millium in The Legend of Heroes: Trails of Cold Steel is supposedly 13 but acts more like a six-year-old, often acting like an impulsive, hyperactive child and tiring herself out.
- Sherry Birkin in the original Resident Evil 2 is supposed to be 12, but her personality, voice, and even her size are all more suited to a 6 or 7-year-old child. She's still rather small for her age in the remake, but sounds and acts more like a real 12-year-old.
- Bowser Jr. from the Super Mario Bros. franchise doesn't have his age stated, but he appears to be somewhere around eight to ten years old. In his early appearances in spin off games like Mario Kart and Mario Golf, he would throw a tantrum and cry loudly as if he was four years old. Baby Mario and Baby Luigi, both being younger than Bowser Jr., don't cry as loud if they lose a game and they mostly show distress instead, while Diddy Kong, who appears to be about the same age as Junior, rarely cries loudly and usually just shows disappointment. Junior's Sore Loser attitude was toned down in later games where he now expresses anger and frustration when losing a game.
- Deconstructed in Umineko: When They Cry. The fact that 9-year-old Maria acts younger than she is causes her to be bullied in school, and infuriates her mother to the point of abuse. In the first four arcs, other characters often lampshade how young she acts despite her age.
- The Most Popular Girls in School: Katelynn Zales is seven, but she acts like she's two. The dialogue regarding that matter is at the top of this page.
- Nina Delacroix from Eerie Cuties is 14, but for most of the strip she looks and acts like as if she was half of that age. Justified in that her development has been deliberately stunted to prevent her from manifesting the reincarnated spirit of an ancient and deadly vampire queen. And then subverted when it turned out her older sister was the chosen one all along.
- Sarah of Las Lindas is the youngest and most emotionally immature of the cast (not counting Digit, the AI). Her age has never been fully established (she's somewhere between late teens and early 20s), so this trope or Manchild could apply.
- The Nostalgia Critic admits to being bullied at school for acting younger than his age. This serves as foreshadowing, as later he realizes from a bad phone call to a director that he's not acting like a normal twenty-eight-year-old man should.
- Jeffy Jeffy from SuperMarioLogan is a teenager, yet plays with children's toys and acts like a hyperactive five-year-old. Not to mention, he still wears diapers.
- Steve Smith from American Dad! is a Depending on the Writer version of this. While most of the time he acts like your stereotypical Hormone-Addled Teenager, some episodes give him childish mannerisms and interests such as toys and playing pretend. He even still has a babysitter in one episode, in spite of being around the same age as her.
- Macie turns into one in the As Told by Ginger episode "Family Therapy" after her parents start treating her like a four-year-old after forgetting her birthday. She starts to enjoy playing on a Rocket Tykes Swingset and a My First Jungle Gym, going to the local Suck E. Cheese's, has her thirteenth birthday party at a petting zoo (with kiddie-style decorations), and even starts dressing more like a four-year-old. Ginger notes that Macie is liable to get bullied if this continues, and repeatedly tries to fix the problem. Macie gets annoyed at Ginger's intervention (and ends up being proven right when the most popular kids in school think the petting-zoo party is some sort of post-modern statement and dub it the coolest thing they've ever seen). In an interesting subversion of the trope, the episode ends with Macie admitting that she knows this behavior is far too juvenile for her: she's just making up lost time with her parents, and assures Ginger that she'll be talking with them about treating her like a teenager soon. Given that she ends up back to her old self, this presumably works.
- The Batman: Batgirl is high school aged, but she acts (and looks) more like a middle-schooler would, especially with how she bickers with Robin, who's at least a couple years younger than her. Though she does mature noticeably in the fifth season when she's a college freshman.
- In the Western Animation/Braceface episode "Act Your Age" 14-year old Sharon dates a boy named Pablo and it turns out he's only 12 years old. However at several points in the episode he behaves like someone younger than that, he wears shoes with velcro (which most boys his age don't) and his 13th birthday party has clowns and loot bags (something Sharon even mentions her younger brother doesn't have at his parties anymore) Most boys that age would think they were too old for something like that. However, this is justified to show how much younger he is than Sharon.
- Something is not right with Cleveland Jr. from The Cleveland Show. Most people just view him as an optimistic nerd, but he also can't let go of some childhood memories. He still plays with his "Larry the Leopard" stuffed animal, and acts as though it's a real person, he often gets easily tricked by Rallo, who is 5 years old, and he wants his dad to kiss him goodnight. This is explicitly stated as weird in-universe, and others his age typically avert this trope unless it's funny.
- Almost every member of the Codename: Kids Next Door is an exaggerated stereotype of children, even the nine- to twelve-year-old ones who should be more mature. They all love soda pop, hate vegetables, and act rather innocent.
- Dexter's Laboratory: Dee Dee, who is elder to her titular brother, is implied to be a sixth grader. This would put her actual age somewhere between ten and twelve. However, she tends to behave as if she were much younger than Dexter, always invading his secret laboratory, acting nosy to Dexter's business, and crying quickly over being snapped at. In terms of her more child-like aspects, she's a Girly Girl who performs ballet, loves the color pink, ponies, and stuffed animals.
- Chris from Family Guy, Depending on the Writer. Some episodes will have Chris behave like a normal teenager, which has become more common in recent seasons, and others will make him easily entertained and somewhat shallow minded, as well as playing childish tricks anybody his age could see through, at age 15. Since his father is a Manchild, and since he is very similar to him, it may run in the family.
- Cubert from Futurama is a 12/13-year-old who looks and acts like he's around 9. A plot point of one episode was about how he felt the need to imitate everything he saw on his favourite TV show, even if it didn't make sense.
- Harold from Hey Arnold! is arguably one of the most immature characters in Mr. Simmons' 4th grade class, as he often cries and has been shown playing with a Barney Expy doll on multiple occasions, and yet he's actually four years older than the rest of his class, since he celebrates his bar mitzvah in one episode.
- Jellystone!: Auggie Doggie is eleven years old, yet she's totally okay riding around in a stroller and her Establishing Character Moment has her scream-singing a song about kittens to cheer up a lady in the hospital. Possibly justified due to Doggie Daddy's comedic overprotectiveness, but still. Parodied in "Mr. Flabby Dabby Wabby Jabby" when Shazzan says that the kids are too young and innocent to watch a horror film, and should instead watch a movie that appears to be about actual babies.
- Jimmy Two-Shoes is a teenager, yet he's very excitable, gullible, and childish and seeks for fun wherever he goes.
- Kim Possible: Ron Stoppable tends to dip into this territory. A prime example is in the episode "Coach Possible" where, unlike most high schoolers, he doesn't mind hanging out at the local Suck E. Cheese's and is horrified when the villains steal, then redress his favorite animatronic. "PIZZAPOTAMUS!!! NOOO!!!"
- Bobby Hill of the later episodes of King of the Hill. Even though he is supposed to be 14 years old, he occasionally acts very childish. This is mainly a case of Depending on the Writer; in some episodes he is fairly intelligent and mature and in others he is incredibly whiny, foolish, and immature. The 13th season has some of the worst offenders, with episodes like "Master of Puppets" and "Reborn on the Fourth of July".
- The Loud House:
- Downplayed with 11/12-year-old Lincoln Loud, who mostly acts his age, but owns a stuffed rabbit named Bun-Bun, which he cares for with an affection most kids his age would have outgrown.
- Leni, the second of Lincoln's older sisters, is 16/17, but due to being The Ditz and having a short attention span, she's often entertained by things commonly used for small children (like finger painting in "Schooled!" and a kiddie puzzle in "Lock and Loud"). In "Changing the Baby", she cries like a baby and even says, "Agoo".
- Luan is 14/15 years old, yet has a fondness for puns, pranks, clowns, novelty toys, and childlike comedy in general.
- 13/14-year-old Lynn is not above throwing tantrums when she doesn't get what she wants, and exhibits very poor sportsmanship for a Passionate Sports Girl. Her childishness is particularly exhibited in "Cereal Offender" (where she rides on a shopping cart and wrecks many aisles at a supermarket), and in "Sitting Bull" (where she plays on a tire swing in the backyard with her younger twin siblings, 6/7-year-olds Lola and Lana, which her four older sisters deem her immature for).
- CJ Casagrande is another 13-year-old who likes playing pirates with his family and Lincoln. In this case, CJ's behavior is justified because he has Down Syndrome.
- Lincoln's best friend Clyde McBride also has a shade of this, since he's a fan of Blarney the Dinosaur (an Expy of Barney & Friends), which is aimed at a much younger age demographic than him.
- Charlotte from Making Fiends is a 4th-grader with the mindset of a pre-schooler, showing a considerably egregious imagination, enjoying toys and games most children of her age would have outgrown from, singing childish songs, and being overly optimistic about pretty much everything.
- Max from Max and Ruby starts out at 3 and speaks in one word sentences. As a 4-year-old he speaks in complete sentences but not in fluent English. He is the only kid in his class unable to do so.
- Moral Orel:
- Shapey, Orel's younger half-brother, is seven years old, but behaves like a toddler. Unlike most examples, it isn't treated as normal, as it's clear that Shapey's issues are the result of his dysfunctional household. In the Distant Finale, it's implied that he was able to outgrow it and become a functional adult.
- Orel's father, Clay, was shown to also not act his age, acting like a 5 or 6 year old when really he was 12. This was because his mother spoiled him rotten, and all the attention she gave him made him constantly act like her precious little baby, which greatly annoyed his father.
- Miraculous Ladybug: Chloé Bourgeois is 14/15 and very much behaves like she was 6, still carrying around a teddy bear and believing in things such as Santa Claus and cooties as well as having the temper of a literal spoiled child. Most of this stems from her Missing Mom and her father constantly enabling her behavior. Neither parent however is willing to own up to this.
- The Owl House: Luz Noceda is a high school-aged teenager and has the rowdiness, wonderment, and imagination of a child at least in their elementary years. She has even played with dolls at her current age before and is interested in action figures. Justified, as it’s revealed that her fixation with her fantasies partly stems from years of social isolation from her peers, pressure from society’s expectations and, most importantly, from her grief following the death of her father at young age.
- A Compressed Vice in the Recess episode "Bonky Fever," where Mikey becomes obsessed with Bonky the Dragon (a parody to Barney), and starts to act more and more childish as time goes on. This includes crying like a baby after getting gently tapped with a dodge ball, throwing a temper tantrum in the cafeteria after the lunch lady refused to give him an extra pudding for his Bonky doll, and asking T.J. to walk him to the bathroom so he can "go potty." This is because he's turning ten, and he's starting to realize that Growing Up Sucks.
- Rosie's Rules: Crystal boasts about how she's 12 and very grown up, only to squeal seconds later when she sees balloon animals. Justified, as a preschool show requires that pretty much everyone act childish.
- Rugrats: Downplayed for Chuckie. He's two, and while he mainly behaves like a two-year-old, the only word he can say to the grownups is "No".
- The Simpsons:
- Ralph Wiggum is this combined with Cloudcuckoolander and ambiguous disorder, he often acts more like a four or five-year-old rather than an eight-year-old.
- Bart Simpson in several later season episodes is often seen acting far younger than a ten year old, most likely as a result of having his Bratty Half-Pint characterization Flanderized. This is emphasized by Marge and Lisa buying him easy reader books and videos meant for very young children.
- The Sonic the Hedgehog (SatAM) version of Tails is intended to be ten years old, which would make him older than his game counterpart, who is stated to be eight. However, he acts as if he were junior to his game counterpart; Tails is not allowed to be a Freedom Fighter for his own safety, which closely matches the way adults would realistically treat a ten-year-old, but it still doesn't explain his immature personality. He also calls Sally "Aunt Sally" despite there only being a slight age gap between them.
- South Park: This is part of what makes Eric Cartman such a terrifying (and hilarious) Anti-Hero. Despite being around nine or ten years old, he is extremely juvenile at times—he throws violently angry temper tantrums when he does not get his way, is obsessed with sweets (in one episode, he claims to have psychic powers, then demands ice cream and cookies in exchange for using his "gifts" to help the police), and still loves to play with stuffed animals and dolls. Part of the reason is his parenting—his mother Liane endlessly coddles him and treats him as her "little poopsykins," so he doesn't have to grow up (although she does gradually get better at disciplining him).
- Pearl from SpongeBob SquarePants may be a teenager, but she dreams about having tea parties, and on occasion, she makes drawings of sea-unicorns.
- Steven from Steven Universe has a Vague Age for the first season and a half, but in "Steven's Birthday" is revealed to be turning fourteen. His Muggle Best Friend and Love Interest, who's not even thirteen but is more mature, is shocked. Aside from the fact that he still sleeps with a teddy bear and generally acts like he's under eleven, Steven also looks quite younger: because his mother was an ageless alien whose species have their physical forms match their mental ages, this ended up applying to Steven as well, with his dad showing Connie a scrapbook showing that Steven hasn't physically aged since he was eight. Future would finally have a more mature (but emotional unstable) Steven who finally looks his age (at that point, 16).
- Teenage Mutant Ninja Turtles:
- In Teenage Mutant Ninja Turtles (1987), they’re more like Tweenage Mutant Ninja Turtles at times. It actually kind of depends on the writer; some episodes they act age-appropriate or like grown men.
- Mikey in Teenage Mutant Ninja Turtles (2012) is this, especially compared to his brothers. "Journey to the Center of Mikey's Mind" shows that Mikey is a little kid in his mind and still has yet to mature, despite being a teenager, which is why he can charm Leatherhead and why he never thinks ahead and refuses to take blame (see "Mikey Gets Shellacne").
- The main characters of Tiny Toon Adventures are treated as teenagers, and in their less wacky moments usually act like them (though it fluctuates). But never Dizzy Devil, Lil Sneezer, or Elmyra, who, despite being in the same class as the other characters, consistently act far younger than they ought to (which doesn't stop Dizzy from having multiple attractive human girlfriends.)
- Hank and Dean Venture in The Venture Bros. are around sixteen when the series begins, and yet their behaviors and speech patterns are on par with those of elementary schoolers in a 50s sitcom. This is mainly played for laughs in earlier seasons, mocking squeaky-clean supposed teenagers in older media, but it becomes increasingly justified later, as it's revealed just how horribly sheltered their upbringing is and that they've lost a fair bit of life experience as a result of being clones. By the fourth season, they end up forced to mature somewhat, though they're still a few years behind their peer groups.