Kids should be kids, at least that's how the saying goes. That means worrying about little kid things and doing little kid things, such as playing on the trampoline, watching TV, going fishing, or whatever it is that kids do locally. What we don't expect kids to do is to drink alcohol, smoke, have sex, use drugs, hitchhike, commit violent crimes, or do other things we associate only with teenagers or adults. Yes, many adults are upset when a teenager drinks beer, but it's disturbing when a 10-year-old does it.
In fiction, there's two ways this tends to occur. Sometimes the kid is shown engaging in such behavior as though it's normal for them, and this can be used to show that the child has had a harsh upbringing. Other times, the kid is trying an "adult" behavior for the first time, which may sometimes have disastrous consequences.
The Creepy Child, the Enfant Terrible and the Evil Orphan draw much of their force from this. From the Mouths of Babes is the Sub-Trope where the child only says troubling unchildlike things.
The Fille Fatale is considered this less than is plausible, since sexual precociousness is often a sign of sexual abuse.
Child Soldiers are a particularly tragic and horrific example of this.
For when kids see things (or have things happen to them) that they shouldn't instead of do things they shouldn't, see Harmful to Minors. A Teenage Wasteland runs on this.
Contrast with Wise Beyond Their Years, which is about positive strangely-adult behavior, and Acting Your Intellectual Age, which is neutral.
Note that if the kid is Really 700 Years Old and just has the physical appearance of a child, it doesn't count. This is for when actual children are the ones engaging in the unchildlike behavior.
This is Truth in Television insofar as there are indeed preteens out there who smoke, drink alcohol, have sex with each other, and so on. This is often the result of a neglectful or abusive family.
Examples of kids engaging in such behavior as though it's normal for them:
open/close all folders
This hilarious condom commercial. It shows a five year old getting a tattoo, cutting his teacher's chair with a chainsaw and being stopped by the police after stealing a car. He continuously explains that his mom said he could. It turns out he'd overheard her cry out "Yes! Yes! Yes!" during sex in another room and assumed that she was replying to him.
Black Jack: Good God, where did you learn that kind of language?
Subverted in Monster. Dieter tosses back a shot like a pro, then jauntily salutes the rest of the patrons as he leaves with a toothpick in his mouth. Once outside, though, he immediately begins retching and questioning the sanity of adults who drink that stuff for fun.
In Soul Eater, Medusa takes over the body of a little girl after she is nearly killed by Stein. The trope is in full swing when the girl's mother notices that her behaviour has been really unsettling for the past few days...
Lucy (and to an extent most of the Diclonii) in Elfen Lied are extremely homicidal little girls. Not helped by an evil DNA voice telling them to kill, the power to kill people really easily, a child's undeveloped sense of right and wrong, and on top of that most of them have been locked up by the government, who have been running horrific experiments on them for the hell of it.
Black Butler has Ciel, an aristocrat living in Victorian London. At the mere age of 13 (he starts off 12, but turns 13 early in the series) he is the head of the household, runs a successful toy and confectioneries company, and is the "Queen's Watchdog" which sends him out on often very dangerous and frightening missions such as helping to catch Jack the Ripper. Personality-wise, he's bitter and jaded... but his darker view on things is because of a traumatic past experience. Still, he's an Improbable Age character. Oh, did I mention he will command his awesome butler to kill people without a second thought? In the manga he's also seen drinking champagne with his guests, but that could be because of his status, the time period, and the overall culture back then which wouldn't have batted an eye at this.
Alois as well. For the whole first episode, he goes from acting completely innocent to downright crazy within a few seconds, and switches back and forth between the two personas. Not to mention how he acts as if he is trying to seduce any male character within five feet of him.
Hansel and Gretel from Black Lagoon. The sheer number of people they kill (and how they do it) is just the start of how messed up these two are. And tragically, they can't even imagine the world any other way.
Probably Revy. From what can be gathered from the tiny flashbacks, she was raised on the streets of a less-good place inNew York City and probably learned her gun skills from gangsters, and killed someone her own father, to be exact using a pillow as a silencer when she was still pretty young.
Kenshin (then known as Shinta) too, when he buried all the bodies of his guardians and the men who killed them, instead of, say, trying to find help. At this point he'd already seen one set of parents die of illness and then watched his Parental Substitutes die trying to protect him. Hiko is visibly disturbed by this and decides to take in the boy since it's clear he'll never live a normal life after this.
Japan Tengu Party Illustrated has a disturbing relationship between a Tengu man and the human child he kidnapped ostensibly to be the vessel for their leader (when he uses her to speak, he swallows her and uses her as his tongue). The child manages to escape the tengu, but the kidnapper is still concerned and obsessed with her. He eventually finds her phone number during a battle, but she never wants to see him again, and besides she's already safe in bed - with her teacher (she likes "magicians (the teacher) better then monsters (the tengu)") note "Real Life" tengu are notorious for kidnapping children and returning them (if they do at all) "in a daze", and tales of monks (tengu dress as mountain aesthetics) and their child-novices don't even bother with Unusual Euphemisms.
Vincent in Pandora Hearts. Taking scissors to stuffed toys? Indicative of problems, but not completely unheard of. Taking scissors to the eyes of Alice's cat? That's not a good sign. It also borders on Psychopathic Manchild behavior since he still does it as a young adult.
In confusing flashbacks and illustrations, Alice or more accurately, the Will of the Abyss... sometimes... also does this, displaying somewhat unsettlingly flirty behavior◊ with Jack and being cheerfully vicious with Vincent. Eventually leading to yet more of this trope from Gilbert, who tries to strangle her.
Recent chapters reveal that Alice is actually an aversion. In her human form, Alice (white dress) is actually the Will of the Abyss with a huge crush on Jack. Alyss's vicious interaction with Vincent is actually a result of Jack's manipulation (even though she does sound awfully cheerful about it). Alice (black dress) is actually a pretty normal girl herself. She just prefers Glen to Jack because of the destruction of her plushie in the real world and Jack's eventual causing the tragedy of Sablier. Her creepiness in Jack's memoirs is a more likely a case of Unreliable Narrator considering what we learn about him later. The Will of the Abyss may qualify for this trope in her scene with Break but that aspect of her personality never comes up again.
The first time we see Akane Awakusu in Durarara!!, she's gleefully chasing down Shizuo with a heavily modified stun gun and shouting "Die!" It turns out that this isn't exactly normal for her, as she was a Cheerful Child before she ran away from home and only did it because Izaya told her that Shizuo was an assassin who would kill her family.
In Project ARMS, there are quite a few children who end up this way, mostly because the Egrigori are very into using them for evil and dangerous experiments. The first ones we see are Al and Jeff Bowen, who attempt to blow up a high school partly for their mission, but moreso because they themselves were teased in school. Al spends the rest of the series methodically working his way through various battles and trying to kill a Keith with a gun at one point. Also, a flashback shows us that the twins murdered their own parents and killed a bunch of kids at their school with a poisonous gas that they invented to leave no traces. Then we get Carol, an adorable little girl who is introduced cheerfully telling Ryo that she has the power to twist and crush things like metal and human bones with her mind and that she very much enjoys the power that comes with doing this. It's implied that she only went through life by having people fear her, and Ryo calls her bluff on her enjoying it. Finally, we get Dark Alice, who is furious at the world for causing her death and is willing to nuke the entire planet to get her revenge.
Broly in the eighth Dragon Ball Z movie was shown in a flashback to destroy a planet, and then laugh hysterically as his father attempts to restrain him, all while he's a child. It's implied that this behavior stemmed from the trauma he endured on the day of his birth (Kakarot [Goku] crying next to him, his narrowly surviving execution by King Vegeta simply because the latter feared Broly's abnormal power level [he was born with a power level of 10,000], and later narrowly escaping Frieza's destruction of Planet Vegeta with his father.
Broly is an extreme case, but Saiya-jin children in general are pretty disturbing by human standards. Originally, Kakarot was sent to Earth to wipe out all life forms. They may look cute and innocent, but looking is as far as it gets.
Played for laughs with Shin-chan, a preschool age boy with the libido of a middle-aged man, who constantly hits on hot women. His baby sister Hima is also occasionally shown to find grown men attractive.
However in the beginning, at least in Konoha, children genin are basically public service workers for the village. D-Rank, which is what they get the most? It basically consists of dog walking, babysitting, weed pulling, etc. C-Rank, which they rarely get is basically escort duty to protect caravans or VI Ps against bandits (which they can easily deal with without killing). B-Rank and above, which are normally reserved for Chunin and Jonin (the more experienced and older ninja), Konoha Genin aren't supposed to get. Which is why the Wave Arc mission was peculiar since it was billed as a C-Rank, but in terms of difficulty and the danger was a A-Rank.
In the beginning Naruto himself is especially fond of doing inappropriate things like sneaking into girl's bathing rooms and turning himself into a naked blond girl for laughs.
Attack on Titan practically runs on this trope, between its use of Child Soldiers and very angry protagonist, Eren. His backstory involves having brutally murdered two men at the age of nine, and justifying it by pointing out that because they were murderers engaged in human trafficking, they weren't people anymore. Then we learn that the people that carried out the attack on mankind in the first two episodes were a 12-year old boy, a 12-year old girl, and an 11-year old boy.
The students of class 3-E in Ansatsu Kyoushitsu. They are tasked with the mission to kill their own teacher and instead of displaying fear or hesitance, they show a great enthusiasm in planning how to kill him. Even more disturbing in that even after they've bonded with said teacher and developed affection for him, it didn't slow them down for a bit. Granted, the fact that their target is not human may be a factor in this behavior, but still, as another teacher had said, this is not normal:
"A group of junior high students are joyfully discussing an assassination. If you look at it normally, this is the pinnacle of madness."
And among them, there is Nagisa, who displays this trope on an even higher level, as it had showed that he will not hesitate to kill even if the opponent is human.
Teenage Sawa Nakamura in The Flowers of Evil frequently does stuff like this, including her manipulating of Kasuga, as well as her scribbling in her journal. As well as some of her "larger" plans as well as her attempts to "get to the 'other side.'"
In Revolutionary Girl Utena, 13-year-old Kozue Kaoru has sex with numerous adult men, once pushed someone down a flight of stairs, and is generally extremely troubled. Meanwhile, Nanami Kiryuu, also 13, has a Yandere obsession with her older brother, and it's revealed that when Nanami was 6 years old, she drowned her brother's cat because she felt he was paying more attention to it than to her. All of this is basically played for tragedy and horror.
Damian Wayne in Grant Morrison's Batman. He's a ten-year-old who is firmly convinced that he's the natural successor to his father's legacy and Dick Grayson is an idiot. In addition to being a particularly grim (and potentially deadly) Robin, he is frighteningly efficient at running Wayne Enterprises.
With Damian, several characters acknowledged it was a bad thing. Bruce originally didn't let him out in the field, and he only became Robin under Dick. Dick got him to act a little more normal though Dick's extreme own personal combo of experience, patience, and just being a good person. Stephanie, after learning Damian had never really played in his life, pretty much forced him onto a moon-bounce with her (though she admitted she was pretty sure he wasn't joking about stabbing her several times during her run) and usually ignored him when he got bratty. Damian acted a little more like a kid around Colin Wilkes (probably to put Colin, who was the same age, more at ease), but it was a major change form his original characterization.
Tim and many other people still found him very unnerving even by the time of the reboot, though.
One of the major themes in Batman and Robin from the New 52 reboot is the difficulty Bruce is having in keeping Damian under control.
Minor Batman villain "The General" was a boy-prodigy that was obsessed with military tactics, and used them to gain a foothold in Gotham's criminal world. That place has the worst luck, doesn't it?
Well-Intentioned ExtremistAnti-HeroAnarky is an intelligent, politically-aware would-be terrorist whose tactics against the corporate elite and the gears of the state range from "hacktivism" to straight-up bombing. He started doing all this when he was twelve.
Kick-Ass: If you are in any way associated with organized crime, Hit-Girl will brutally chop you up and shoot you in the head while cursing like a sailor. She's a cute 10 year old.
A short scene in the filminverts this for a while. Her father is very disturbed that she is acting like a normal girl, until she reveals she's screwing with him.
Crossed children appear to be no less foul-mouthed, kill-happy, or rape-happy than their adult counterparts.
The latest version of the Hellfire Club in X-Men. Members include a boy who sold his seven brothers into intergalactic slavery to claim the family fortune and another who dissected his first Atlantean when he was eight. The leader is a Self-Made Orphan.
Recurring but lesser-known villain The Gorgon from Marvel qualifies; though it's not shown, he was described as being born with near-full-adult intellect, saying his first words at two weeks, walking at three weeks (and only took that long because his body had to build up) and being fully literate before his first birthday. He also first tried to commit suicide at age six, shortly after writing his first opera, and mathematically proved the existence of the One-Above-All by 13, three more suicide attempts later due to realizing how utterly insignificant and worthless not just himself but the entirety of humanity was to the universe at large. "Prodigy" barely covers his mental ability, and if he hadn't developed the mutant power to turn people to stone by looking at them (hence the name Gorgon) and hooked up with HYDRA around the time most of us are just starting to plan for college, he probably would have ended up successfully killing himself.
X-23's first assassination was at age 9. She was immediately put to work by the Facility afterwards, and by 16 she's an accomplished enough killer to worry Captain America. Justified since she was bred and raised from birth specifically to be a Living Weapon, but her utter ruthlessness and cold detachment makes her an even better killer than Wolverine. It's mildly subverted in that she doesn't want to be a weapon, but it nonetheless comes completely naturally to her.
In Marijuana Simpson Maggie can't be older than ten, yet she smokes pot constantly with the rest of the Simpson Family.
Rose Potter (from The Girl Who Lived septology fame/infamy) murders Professor Quirrel at the age of eleven, and encourages her friends to use lethal force by the age of fifteen. She's also in an active sexual relationship by about that time.
Commander Adriatic Huxton of the "Battlestar Galactica" fanfic "The Long War" seems to have this in his backstory. He so far has been attributed to killing a couple partially responsible for the death of his family, when he was five years old. Given that after this he would have been living alone in a ruined city and that he's a paranoid schizophrenic, there's a good chance that he's done more.
Later on, in the Gensokyo 20 XX series, we have Reimu. Being mentally reconditioned to and being so detached from pain stimuli as a result, she has been noted to be harming herself, something that a normal person wouldn't find from a three year old, not one without severe mental or behavioral problems, unless otherwise. To top it off, Reimu has a habit of hitting, scratching, and biting others, apparently, unaware that the others can and do respond to pain and injuries or she is merely trying to relearn how to feel and respond to pain, though the former is likely than the latter.
In 20XXV, it was noted she had tried to stab someone with scissors but it is never known why, then again, she is suffering from kind of mental illness. In chapter 82, she does succeed in stabbing Yume Ni with a pair of scissors and that was after the latter kicked her in the face.
In that vein, we have Yume Ni and she is noted to be fairly violent for a child, this even escalating to a degree that she tried to toss Reimu over railing without a second thought as to whether or not that could kill her and this isn't first time she has actually been that cruel to them, though the trying to kill Reimu thing ism't arguably new, seeing as she did come close to seriously injuring the other kids.
In Kill la Kill AU, we have an eight-year old juvenile delinquent Ryuuko smoking, as well as the fact that she has led a life of crime, earning the nickname "Repeat Offender". In that vein, we Nui, Mako, and Nonon who are also delinquents and they smoke, as well as the fact that, as a first time offender, Nui has gotten multiple charges, to which she shrugs off like it nothing.
Frank Berkman in The Squid and the Whale. Twelve-year-old Frank drinks beer and — most disturbingly — appears to fantasize about raping his mother. It's unclear whether this behaviour is normal for him or is a response to the tension in his life at that point (his parents are separating, and all of this takes place on a day when they've accidentally abandoned him at home alone).
Thelma and Elizabeth in Little Sweetheart. Both of them are guilty of stalking, theft and blackmail. Elizabeth also mentioned watching porn on TV at one point (it was 1989). Thelma is solely guilty of attempted murder and using a cop to murder someone and filing a false police report.
Hailee Steinfeld's portrayal of the 14-year-old Mattie Ross in the Coen brothers' version of True Grit is, even though she isn't a child anymore, very disconcerting in its seriousness and vengefulness.
The controversial Hounddog has Lewellen, its 11-year-old main character, drinking alcohol. This is considered normal in her family.
The movie Young Thugs: Nostalgia has protagonist 6th grader Riichi Nakaba get drunk twice in the movie. In one scene his family and the guests at the party encourage him to get drunk.
The movie Sugar Cane Alley has eleven-year-old Josť Hassan and his friends (one a girl who is probably no older than eight bought the vodka and said it was for her parents to the clerk) get so drunk that they laugh as they set a shack on fire.
The sex worker Iris in Taxi Driver gives off an aura of grace, poise, and sexually-charged sophistication. She's also twelve. Jodie Foster's performance was by far the most unsettling thing about the film, even overshadowing de Niro's own performance as the increasingly sociopathic Travis Bickle.
And Jodi Foster again as the murderous and seductive Rynn in The Little Girl Who Lives Down The Lane.
Hard Candy runs on this alarmingly. The protagonist tracks down, incapacitates, tortures, and drives a pedophile to suicide. She's (allegedly) fourteen years old. Originally it was planned for her to reveal at the end of the movie that she was really 18, averting this, but the line was cut and her exact age is left ambiguous.
In the 2005 adaptation of Tom Browns Schooldays, Dr. Arnold is shocked that the students, some as young as ten or eleven, gamble, distill liquor, and keep guns.
In City of God Lil Dice goes on a shooting spree in a hotel. Also, many children are involved in the gang war. (Horrifyingly enough, this is more or less Truth in Television.)
In Sweeney Todd: The Demon Barber of Fleet Street, the title character finds Toby easy to bribe with gin. As Toby tells Mrs. Lovett, they used to give the stuff to kids like him in the workhouse (child labor laws didn't exist way back when) so they could sleep — though as he mentions, you wouldn't ever want to sleep there, "not with the things that happen in the dark."
Don't forget the ending, when he coldly and quietly slits Sweeney's throat.
Lawn Dogs has a lot of this. Not to mention some in the form of Corruption by a Minor, as Devon manages to convince her adult friend to steal chickens from a barn, and later, moon her father. And no, Devon is not portrayed as wise beyond her years either. She otherwise acts like a normal preteen girl, who happens to do some messed up stuff, in a realistically childish way.
"Also, children are expected to be a certain way, and I like the unexpectedness of how children really are if you watch them. (...) Sometimes children just don't go by the rules, they often have a natural inclination not to, which we as adults have often lost." - Naomi Wallace, screenwriter for Lawn Dogs
In The Good Son, 12 year old Henry (played by Macaulay Culkin) smokes, drinks alcohol, vandalizes property, builds homemade weapons, conducts horrible schemes, tortures and kills animals, and kills people all like it's an everyday thing.
Speaking of Leonardo DiCaprio, he himself had portrayed a 14-year-old Catholic school boy's descent into heroin-addiction and prostitution in order to support his drug habit in 1995's The Basketball Diaries.
Total Eclipse, another Leonardo DiCaprio movie (boy, he surely went through a phase of acting in edgy, indie roles in 1995...). He plays Arthur Rimbaud, a wild and bratty teenager who gets into a sexual relationship with an older, married man. The entire movie highlights how sick and twisted their relationship is.
Let's not forget scamming, scheming, stealing, swearing, smoking little Addie in Paper Moon.
In RoboCop 2 there's Hob, the villain's main henchman, who is a boy of about 12 and very competent too.
Tideland consists entirely of this, although Jeliza-Rosa does not fully realize everything that's going on around her and keeps acting and (probably) thinking like a child while she does stuff like preparing the syringe for her drug-addict father and seducing a grown man. (Thankfully, he's mentally about the same age, but it's still very, very disturbing.)
Another Chloe Moretz film, Hick, runs on this. It starts with its 13-year-old protagonist running away from home to live in Las Vegas, bringing a gun with her... and it gets worse from there.
Trish from Angels Revenge, though it might be justified since she's a young teenager. She gets just a little too excited at a drug dealer's unwanted bris, she latches onto another drug dealer's car in order to track him, and she fatally shoots a kingpin at the end of the movie.
Pretty much the entire cast of kids in Twelve And Holding.
River Tam in Serenity. Better than 50% of the on-screen kills are hers. She's a teenager.
Battle Royale is disturbing enough... until you consider that (apart from Kawada and Kiriyama) they're ninth graders, no older than fifteen! Many of the characters take great delight in killing others, even if not all of them want to.
James (later Agent J) in Men In Black uses this to justify "why little Tiffany had to die" in the recruitment shooting gallery; she had quantum physics books which were "way above her reading level" and that she was "about to start some shit".
In Kill Bill, The Bride, before going off to exact her final vengeance on Bill, babysits a young girl who is her daughter B.B.. She asks the girl if she would like to watch a video before she goes to bed. The girl's answer? Shogun Assassin. Being a former member of the Deadly Viper Assassination Squad, The Bride sees nothing wrong with this, so they watch Shogun Assassin together.
The title character of Eve's Bayou runs on this. She curses, tries to kill her father, Loui, and sneakily reveals her father's affair to his lover's husband, which eventually leads to Louis' death. The fact that she's named "Eve" and has repeated associations with apples and snakes is just icing on the cake.
It's 4 AM, and a little kid stands on a street corner in Soho with a flattened frog on a rope. A copper comes around the corner and says "'Ello, sonny, what are you doing out here at this time o'night?" The kid replies "I'm lookin' for a whore." The copper, flabbergasted, asks "How old are you?!" The kid replies "I'm nine, right." The copper then asks "What do you want a whore for?" The kid replies "I wanna get a disease." "What kind of bloody disease?" the copper inquires. "A sexually-transmitted one, officer." "What on earth do you want a bloody disease for?" "Well, if I get it, I go 'ome and I fuck the babysitter and she gets it, and she fucks my dad and 'e gets it, and 'e fucks my mum and she gets it, and she fucks the gardener, and 'e's the cunt I'm after 'cuz 'e squashed me frog!"
The Animorphs books: The animorphs are kids. They kill people.
The novel The Bad Seed was very controversial, portraying, as it did, a pre-teen girl who's a multiple murderess.
Addie Pray, the novel on which the movie and TV series Paper Moon was based, is narrated by a pre-teen girl who's a full-fledged swindler learning from an established con man.
Duumvirate lives and breathes this trope. Even the littlest kids are perfectly willing to kill at the drop of a hat. It's all just a game to them.
Rather freakily lampshaded in Brave New World, where the childhood conditioning all the citizens are exposed to encourages children to act sexually towards each other at about pre-school age. The people administering said conditioning laugh about how those poor unenlightened souls way back when would have treated such behavior as disturbing.
This is derived from a misinterpretation of Freudian psychology (see also Oedipus complex) that was more common in earlier decades and spawned several pro-pedophilia groups. The notion peaked in the late 1960s, when "free love" was all the rage but modern notions of consent hadn't been thoroughly formulated. All the more disturbing, no?
Although not really a disturbing or creepy example, in one of the Discworld novels Nanny Ogg ruminates on the concept of people having "natural ages", levels of maturity they were designed for; her examples are herself, who is somewhere in her eighties but has always felt mentally nineteen or so, while some children appear to have been born thirty-five; she's referring to them being austere and boring rather than engaging in actual adult behavior.
Wensleydale in Good Omens is an example of such a child: "His parents called him 'Youngster', possibly in the hope that he'd take the hint".
Gone , by Michael Grant, has this in spades. The entire cast is aged fifteen and under, and Sam and Lana both dwell on how disturbing it is to see young children drinking, smoking, and doing drugs. Not to mention the plentiful violence.
The Redwall series. Oh, Dark Forest Gates, the Redwall series. The titular first installment features a season-and-a-half year old squirrel — described in the text as a baby and not talking yet — who is personally responsible for the horrible deaths of at least ten vermin, and assists in the killing of many others by rolling a hedgehog over them in the middle of a battlefield. He's also given a sharp dagger by a hare who thinks nothing unusual of a kid stabbing people with one hand and sucking the other. By comparison, the young, gangly teenager that goes on to see new friends and an adoptive father/Abbot poisoned to death, kills massive numbers of vermin, faces and decapitates a snake that could eat him alive, and comes plummeting from the top of an Abbey with a bird stuck in his shoulder, all by the age of thirteen seasons, seems almost reasonable. Oh, and gets married and has a son before he's sixteen seasons. Combines with Angst? What Angst?. This may have been intentional Values Dissonance, as the series is set in pseudo-10th century England WITH FURRIES, but has been somewhat dialed down in the sequels... which still include the slavery of preteen children and the murder of their slavers.
The Tomorrow Series: Aside from the fact that the viewpoint characters are only 16 - 17 years old, and essentially learning to become guerrilla fighters as the series progresses, the group of kids living in Stratton are a more depressing version of the trope: by The Night Is For Hunting, when the main characters meet them, they are well-accustomed to gunfights and mugging people in alleyways.
Her bodyguard thinks it's creepier when she actually acts her age.
Artemis Fowl: the titular criminal mastermind is twelve years old in the first book, fifteen or sixteen in the last.
Enderís Game: Ender Wiggin, at six, beats a bully to death. Because he knows that being merciless will let him win. Although his intention wasn't to kill the bully, just to beat him so badly that he and the other bullies would be terrified of Ender from then on, and thus, leave him alone.
Somewhat justified in that the school he attends deliberately recruits children who act and think "older" than their age in order to train them to be part of the war machine.
The same thing goes for almost every other child character in the book (especially Ender's siblings, Valentine and Peter), who are either unnervingly intelligent, sociopathic, or both.
Tom Riddle from Harry Potter was an ultimately creepy kid. As a child, he tormented his fellow orphans - even murdering one's pet rabbit. When he went to Hogwarts he learned to be sly and manipulative, continuing his evil acts and a couple of murders without being suspected by the older, more powerful wizards who could pose a threat. Then, of course, he became Lord Voldemort.
Arya Stark from A Song of Ice and Fire. Committed her first premeditated murder at age ten. It wasn't her first kill, just the first one she planned out deliberately. Oh, and she's one of the heroic characters.
There's also the six-year-old Robert Arryn, who takes a rather disturbing delight in watching people get thrown thousands of feet to their deaths.
Joffrey Baratheon really takes the cake. At the age of six, he cut up open a cat and to see the unborn kitten fetuses. Later on in the story, he killed peasants from his palace's boarders with his crossbow and told them to go eat their dead, had people fight to the death, tormented his younger brother, and abused Sansa Stark, all before turning fourteen.
In The Iron King, Meghan is shocked to hear her four-year-old half-brother tell her best friend "Go fuck yourself!" Justified in that the kid is actually a changeling. Her real half-brother is a perfectly normal, sweet kid.
Daine in The Immortals series hunts down and slaughters the bandits who killed her family, aged twelve. Justified by her grief and the fact that her gift was making her think she was a wolf, but made more unsettling by the fact that, when she does eventually tell her friends about it, most of them simply shrug it off. Granted, her friends have gone through some fairly dark stuff themselves...
Kel in Protector of the Small is surprised to realize that cheerful, friendly first-year Owen has no problem whatsoever killing bandits. Kel's killed bandits too, but she had been expecting him to at least be uncomfortable with it.
The main plot point of The Hunger Games—teens and preteens as young as twelve are forced into an arena to fight each other to the death. And some of them are disturbingly good at it.
In The Coldest Winter Ever by Sister Souljah, Winter, the 16-year-old daughter of a drug dealer, engages in lots of adult behaviors. For example, she offhandedly mentions that she lost her virginity at age 12, which was kind of late. The novel ends with her getting 15 years in prison for possession of illegal drugs.
Robert Westall's The Machine Gunners presents some examples of this. The plot of the book involves a group of wartime children between 11 and 16 who steal a working machine gun from a crashed plane, hide it from the authorities, construct a bunker and emplacement for it; hiding two of their number from the adults and later a captured German airman in said bunker and open fire on a group of Polish soldiers during what everyone thinks is a Nazi invasion.
In Crooked House by Agatha Christie, twelve year old Josephine investigates the murder of her grandfather, using her naturally snoopy nature to provide clues that the outsiders to the family never manage to find. Then it turns out she's the murderer, having decided to kill her grandfather over his not getting her ballet lessons. She decides to investigate the murder to get further attention from her family and the police.
It's not entirely clear whether the orgy in Stephen King's It is intended to evoke this, but bloody hell, it certainly does.
Darth Plagueis has Palpatine running over two pedestrians. His reaction afterwards indicated that he enjoyed it even though it was his first time.
Five-year-old Kassandra in "The Painter Knight" provokes Oh Crap moments in captured traitors and various other condescending adults when they realize A: she knows what treason is; B: she knows the penalty; and C: she has followers willing to carry it out at her (lawful, if untraditional) order.
Encouraged by Lemony Snicket when asked to choose "Five Books You Should Read Before You're Twelve" for The Big Issue magazine. Four of them are reasonable recommendations; the last is Lolita:
Don't read this, just carry it around. When adults ask "Are you really reading that?" in panic, say nothing and just blink at them.
Lord of the Flies has a lot of this, since the protagonists are British schoolboys who descend into savagery and murder after being shipwrecked on an island.
In one of the Confessions of Georgia Nicolson books, Georgia catches her three-year-old sister Libby doing a hip-wiggling dance and singing to Sex Bomb by Tom Jones. Georgia's reaction is that this is inappropriately sexualized behaviour for a toddler and complains that their parents are turning Libby into a child prostitute.
In Goodnight Lady by Martina Cole, at age eleven protagonist Briony is already a seasoned prostitute (who asked to be sold to a brothel in her sister's place) and has more sense of the "business" than women three times her age; later causing her to become rich and successful as the owner of many brothels of her own.
In the Dollanganger series, Cathy's son Bart develops a sexual fixation with his own mother and tries to kill his adoptive sister when he's still a child of around eight or nine.
In the Casteel series, Fanny has already begun fooling around with boys by the time she is ten. It's implied that she may already be sexually active by this age, as she later seduces her adoptive father and has a baby with him when she is no older than fourteen.
A similar example to Fanny above is Fern from the Cutler books, who displays age-inappropriate knowledge of sex, manipulates her brother into letting her live with him by lying that her foster father sexually abused her, and as an adult is proud of having become sexually active while still middle school aged.
Sylvia Adare in My Sweet Audrina may have killed her father's girlfriend Billie as a young child. It's suggested that Vera set it up to look like Sylvia did it but Audrina can never really be sure.
Ian March in the Early Spring series is a thirteen-year-old boy obsessed with performing "experiments" involving his sister Jordan, who is going through precocious puberty at age seven. He then murders their governess after she tries to intervene. The governess herself is horrified at what she sees as unchildlike behavior from both the kids, since Jordan already knows the word orgasm (although she learned it from an older teenager) and uses tampons, rather than sanitary towels, for her premature periods.
The unnamed ten-year-old girl in the late Jo Imog's The Demon Flower goes from letting older men molest her in exchange for the tinfoil from their cigarette packs, to enacting bizarre scenes with an adult woman friend, to increasingly weird sexual and occult adventures, incidentally driving her mother insane and being responsible for several suicides.
Pretty much all the kids from Chronicles Of Magic, but special mention goes out to Queen Cinder, who not only enjoys torturing and executing her subjects, but has been trained to kill without remorse since she was five. She is now fourteen.
Live Action TV
Angel: The Conduit blithely instructing Angel to snap Lilah's neck... which he moves to oblige, completely nonchalant, until she giggles and calls him off at the last second.
In an episode of Sex and the City, Samantha is jealous of a very rich 13-year-old girl for whom she organizes a Bat Mitzvah party. When she overhears the 13-year-old telling her friends about giving blowjobs to keep a man, Sam interrupts to say that this is wrong. When the 13-year-old replies that she has been giving blowjobs since she was 12 and that she knows how the world works, Sam is released from her jealousy as she realizes that at least she had a childhood.
There's an episode of House where a mother brings her young daughter into the clinic for possible epileptic behavior. House examines the girl, and determines that she's merely been "ya-yaing the sisterhood". The mother is shocked, to say the least, but House says that it's reasonable behavior, if a bit atypical.
Jayne Cobb from Firefly. It's revealed that at ten years old Jayne was shooting spaceport varmints for the bounties, which is marginally acceptable even if ten is rather young to have unsupervised access to a .22 rifle... and using the money he earned to bet on gladiator blood sportsand buy beer.
River Goddamn Tam, most especially in Serenity, but she's hijacked spaceships and shot people (without looking, yet still perfectly accurate) by the end of the show. She's in her teens.
In one episode of Bones, the murderer turns out to be an 11-year-old girl, who shoots her tutor with a shotgun when he refuses to help her cheat on a school project.
CSI: Crime Scene Investigation had one in the form of a 12 year old girl who was taking senior level high school courses. At her older brother's trial for murder of a classmate, she testifies that she's the real murderer and produces evidence to support her case. She pulls off the plan so well that she convinces the court that there is too much doubt to her brother's involvement (mainly, that he was a D student in chemistry and the murderer needed to know how to handle pure Sodium) and that there was too much doubt to convict her (she was too small to move the victim's body). As if that wasn't the worst of it, she says to Sarah that had she been convicted, she could get her degree by 18 and/or write a book about the crime, since Nevada has no "Son of Sam" law. Finally, it was revealed that she had no involvement in the murder and Sarah just got played.
It's even worse in the continued episode later on, when it's revealed her Yanderefixation on her brother prompts her to murder his girlfriend and blame him for it. Her motivation is that it will get rid of any "obstacles between them" and that, by continuously visiting him while he's in prison, he'll fall in love with her. Instead, he kills himself.
Leverage: Poor Parker. Mostly, it's played for laughs, but the ages at which she started committing various crimes is alarming. Car stealing at twelve, and getaway driving before that. Cut to a flashback of what looks like a nine year old Parker skidding around an old lady with a terrified robber in the passenger seat.
In one episode of Grey's Anatomy, a man is brought into the hospital after supposedly being accidentally shot by his six-year-old daughter, using a gun that had been carelessly left outside. However, scans show that this man has been shot 17 times. When the daughter is questioned about the event, she asks why her father wouldn't just die, since she had shot him so many times. As it turns out, the girl and her mother had been putting up with severe abuse at the hand of the alcoholic father. The girl, seeing her father begin another attack on his wife, grabbed the gun (which had been left in an easily accessible place) and shot her father.
Parodied in a Jam sketch where a man believes he has accidentally killed his friend during an argument. He calls a professional killer/"cleaner" named Maria to dispose of the body, but she turns out to be only six years old. She uses language that would make a sailor blush, carries a gun, and when the victim wakes up (revealing that he was only unconscious) she shoots him in the head then hacks him to bits with a saw blade. In the end, the police are called and Maria instantly reverts to a cutesy child act.
Jam was based on the radio series Blue Jam, which featured several sketches about Maria. More disturbingly, in this version she is only four years old!
An episode of Criminal Minds focused on a series of murders of young children. They turned out to have been committed by a young boy (the son of their original suspect), who, in his own words, did it "because I wanted to."
Play horribly straight throughout the series; most preferably by King Joffrey Baratheon, who was a 'very sweet child'...until the age of about 12, when his father told him that pregnant cats had kittens in their stomachs. He mutilated the cat and awarded the fetuses to his Father. It got worse.
Francis Wilkerson, or heck, any of the kids from Malcolm in the Middle, easily qualify. Francis, aside from attempting to douse his teddy bear (as noted in the subtrope "Kids trying this behavior out for the first time" below), also frequently tortured his younger brothers (barring Dewey), stole their toys, locked them in a closet, and scarred Reese with a bayonette, all as a child, and he also implies when telling Dewey this that this is exactly what being a good brother is all about. As a teen, he frequently goes on destructive rampages/rebellions, such as stealing his mother's car, sleeping around, smoking, drinking, getting four nose pierces, and other similar behaviors all just to spite his mother or just for the heck of it. Reese is very much prone to violence, and enjoys hurting people.
The Gallagher Children in Shameless are all examples of this (or were, at some point in the show's backstory), but they run the spectrum from Promoted To Parent "reponsible" types like Fiona and Debbie to absurdly worldly but irresponsible or immature Street Urchin-types like Lip and Carl (who is arguably way more naive than the others). Ian's somewhere in the middle, being self-disciplined and responsible but not taking an active role in raising his younger siblings.
A major theme in The Wire is that the children at the low-rises of Baltimore are already involved in the drug game by the age of ten, even earlier. On the violence aspect, Snoop and Kenard come to mind.
More than one case on Law & Order: Special Victims Unit has been advanced with this trope. The first instance was when Elliot Stabler got blatantly hit on by a seven year old.
Child prostitute Annie in Copper - and that's before she kills the man who killed and raped, in that order, her twin sister.
Although he's an adult when you meet him, on Elementary the antagonist turns out to have been a child when he was kidnapped, but turned the relationship with his captor around to become the dominant partner and had him kidnap and kill other children just so the boy could enjoy seeing the looks on the parent's faces on the news.
In "Brenda's Got a Baby" by 2Pac, Brenda (then 12 years old) gets into a relationship with her 20-somethingcousin after becoming frustrated with life athome. She becomes pregnant, but manages to hide the pregnancy from her family. She ends up giving birth on the floor of the girls' bathroom at school, and tries to dispose of the baby in a dumpster (only to feel bad and take it out). She and her mother are constantly at each others' throats, and finally Brenda is kicked out of the house. She is too young to be hired for honest work and has no place to go, so she sells drugs...until she is robbed at gunpoint and is driven to prostitution. It does not end well.
Similarly, the third verse of Ludacris's "Runaway Love":
Little Erica is eleven years old She's steady trying to figure why the world is so cold So she pops X to get rid of all the pain Plus she's having sex with a boy who's sixteen Emotions run deep and she thinks she's in love So there's no protection he's using no glove Never thinking 'bout the consequences of her actions Living for today and not tomorrow's satisfaction The days go by and her belly gets big The father bails out he ain't ready for a kid Knowing her mama will blow it all outta proportion Plus she lives poor so no money for abortion Erica is stuck up in the world on her own Forced to think that hell is a place called home Nothing else to do but get her clothes and pack She say she's about to run away and never come back.
Metric's song Youth Without Youth is about children engaging in violent behavior and fighting with the cops, eventually getting arrested. The entire song is framed in a way that compares their behavior with different children's game.
My neighbour's kids sold weapons-grade plutonium And frosty, ice-cold lemonade. They took MasterCard and sometimes human organs in trade. That's how we paid. I have to say that it was really darn good lemonade.
Blood Claws in Warhammer 40,000. Granted, they're not actually children (more along the lines of 18+ due to how long it takes to become a Space Marine), but they just came into adulthood and will blindly charge towards a 40' towering monstrosity while laughing their heads off, not exactly behaviour suited to the average teenager (especially since many older warriors would run away in fear from said monsters).
Ienzo from Kingdom Hearts... By looking at him, you could never possibly guess he would be the one to convince Ansem the Wise into building an underground laboratory to experiment with the Darkness in people's Hearts, which eventually lead to the apprentices losing their own Hearts...
Mission Vao, a fourteen-year-old twi'lek living in Taris' Lower City spends most of her time adventuring, thieving and fighting off thugs, slavers and trigger-happy gangsters. Plus, the Outcasts in the even worse Undercity know her as someone who explores places even their scouts fear to read, which means going toe to toe with rakghouls. There was also a significant gap of time between when her piece of ossik brother abandoned her and she started traveling with Zaalbar.
Rule of Rose: Byzantine plotting, power struggles, and even torture are everyday occurrences in the Aristocrat Club of the Rose Garden Orphanage, and depending on the player's interpretation, some of them don't even shy away from murder if they can get away with it. And manipulating a serial killer to commit murders is definite canon for one of the characters, although that wasn't considered typical behaviour even for her.
The imagery of mock suicide by teenagers (and, in one case, an elementary-school kid) in Persona 3 is more than a little disturbing, and likely the primary reason for the game's "M" rating in North America.
Tiny Tina, from Borderlands 2, is the world's deadliest 13 year old and an explosives expert. In her introduction cutscene, she proceeds to blasting a Faceless Goon into oblivion. And thats just the start.
Anise Tatlin in Tales of the Abyss is a 14-year-old Gold Digger, and quite mercenary about it - she speculates on the merits of having to wait on a sickly husband who's likely to die early and leave her his fortune, and throws herself unashamedly at a man more than twice her own age. The fact that this is all Played for Laughsmay or may not make it better.
Mad Father: About 1/4 of the way through the game, Aya finds the Mini Chainsaw. She proceeds to have a nostalgic flashback of the first time she played with it. Also, when one investigates her dressers after the first scene with Ogre, she will find dead animals inside. The fact that Aya doesn't react to this in the slightest implies she already knew they were there (and most likely killed them herself). One of the additional notes from the second playthrough outright confirms this. Also, during the course of the game, Aya will be burning monsters, interacting with corpses and reading other people's diaries.
The gun-toting, cigar-chomper, mad-bomber that is Peacock from Skullgirls definitely qualifies.
The Last of Us has Ellie, a fourteen year old girl who can shoot, swears like a sailor and her biggest reaction to someone being shot to pieces is 'Oh [insert swearword here]'.
The main cast of Higurashi: When They Cry are well-known for their (usually) Hate Plague induced paranoia and murder sprees, among many other troubling behaviors. The four oldest characters are only about sixteen, with the youngest being somewhere between nine and twelve.
Rika drinks wine to drown her sorrows and she's not any older than twelve (at least, not physically). She does this behind everyone else's backs, though.
Plus she also tries to have sex with Shirou at two points in Fate and one in Heaven's Feel. Which is... a little disturbing.
Chelsie Warner, the Creepy Child of Concession. She suffers from gender dysphoria, and was born "Charles" until her parents allowed her to start dressing and living as a girl. This itself isn't what's troubling, otherwise we'd be dealing with Unfortunate Implications, but she displays violent tendencies in her very first appearance by stabbing Artie in the eye with a crayon. She then rapes him when he's too delirious to know what's going on. It was later revealed that her hypersexual behavior was related to a form of bipolar disorder, and she joined a harem of preteen boys run by the practicing pedophile Kate, who specifically seeks out children with this disorder because she believes that allowing them to give in to urges which are already there doesn't count as abuse. The author points out that he knows that it does count, but Kate does not know that or refuses to believe it. Luckily, the "Where Are They Now?" Epilogue shows that by the time Chelsie's an adult she's transitioned fully to female and is much more mentally stable under the care of her adopted father, the local priest Father Tim.
Namah in Dreamkeepers Prelude is a milder version then people on this page, but she still did a Slasher Smile when she went into the ventilation system, stole knives, poured hot sauce in the eyes of one of her guards. Considering that she is being kept in her room to prevent knowledge of a secret affair being leaked, it's kinda justified.
Nadia (and possibly Dark) in Kagerou, although whether they're actually children, or even real, is highly debatable. Their actions are made more disturbing by the presence of Kid, who is very childlike.
The trolls of Homestuck do not, as a rule, have much in the way of childhoods—but some of them develop a strong interest in collectible card games or rainbow drinker romance novels, and others begin earnestly studying for a career in law enforcement (complete with the mass hangings ofscalemate plushies) or become mass murderers by the age of thirteen.
There's also Roxy. Like her Beta counterpart, Rose's mother, she's a Hard-Drinking Party Girl. Unlike her Beta counterpart, she's only fifteen. Of course, she's one of the last two humans on the planet, and was raised by childlike Chess people, so it's unlikely anyone has ever told her to stop except her peers.
Larisa of Sandra and Woo. She likes fire. A lot. She also does things like accusing her math teacher of molesting her to get out of a test, attempt to make out with her boyfriend while he's in the middle of a class presentation, and joke about being a "junkie" when injecting her insulin. All the other girls at school have been warned about her, and her mom point blank asks if she's still a virgin after a class trip. The other medicines she takes and, contrary to the insulin, keeps a secret from her best friends, gives this already uncomfortable behavior some further uncomfortable undertones. We'll see where it leads.
In Apothecia, an eleven-year-old girl kills a child abductor and feeds his corpse to an alien in the woods behind her house.
In Mall Fight, Sakura acts like she is at least sixteen, despite only being nine, and often has sex with her actually teenage boyfriend. The only time she really acted her age was when she was aged down to five a little before the latest reboot.
Some of the Killerbunnies are children but one of them that seems to really stand out is Creameline Rougue and the fact that she sees what she is doing as a game and that Detroit is her playground.
Bonesaw from Worm joined up with the SlaughterhouseNine when she was five. During the story, she's between twelve and fourteen and produces Body Horror on a level unmatched by pretty much any other character. Being a Tinker specializing in biology means that she can do anything with living creatures up to and including bringing back the recently-dead...and those she reanimates would probably rather have stayed dead.
Maggie from The Simpsons is a lot smarter and often ruthless than one would expect from a baby. It's strongly implied she was the one who shot Mr. Burns, after all.
Avatar: The Last Airbender: When we see Azula in a flashback to when she was about 8 years old she engages in typical activities such as teasing her brother and her friend who has a crush on him, doing cartwheels, throwing rocks at animals, throwing fireballs at people, hopefully suggesting that her uncle and cousin might die in battle so her father can inherit the throne, setting dolls on fire, mocking her uncle for leaving a battle after her cousin died, cheerfully telling her brother and mother that her father has been ordered to murder her brother...
We first see Azula, aged ten, in a flashback in the first appearance, smirking with glee as her brother and father have a fight. That ends with her father calling his apologetic son a disrespectful traitor before burning off half of his face for refusing to fight back.
The Gaang itself, while going through the stock hero's journey, has no members older than young teenagers. They command shock troops, lead prison riots and breakouts, rediscover ancient history, and frequently discuss their leader executing the Fire Lord.
Young JusticeInvasion Jade's baby laughs at the fighting she, and Red Arrow are engaging at an army of Mooks. Partly because the baby came from a family of supervillains.
In the My Little Pony: Friendship is Magic episode Ponyville Confidential, Diamond Tiara, the Alpha Bitch of the local schoolhouse, openly engages in blackmail and shows signs of outright sociopathy. ("Feelings? I don't care about feelings!")
Comedian Brendon Burns tells a story about catching his 5 year old son masturbating with a soaped up shark toy, his advice was:
Burns: DON'T DO THAT!
Son: Why not?
Burns: Because adults don't like it when little kids do that, and I wasn't allowed to do it when I was your age and..... y'know what, go ahead, just don't do it at school.
Son: Why not?
Burns: See rule #1. (Rule 1 is "it'll suck, and you'll hate me for letting you do it")
Played for laughs: Catholic speaker Chris Padgett tells a story of when his young son first learned a bad word- "boobie"- and would not stop saying it. Eventually, Chris's older daughter sits down to talk to him:
Daughter: You can't say that word anymore, it's bad.
Son: Yes I can, boobie.
Daughter: Jesus wouldn't want you to say that word, right?
Kevin Smith, on one of the "An Evening With Kevin Smith"s, describes his daughter learning her first naughty word (bullshit) while she was a toddler. Unlike most examples of this trope, this was intensely hilarious to Smith and his wife, who egged her on; she even got creative with it (dogshit, mommyshit, daddyshit). Then they said, "Do you know what 'shit' means?" "No." They told her, and the girl got very quiet...
Many children who grow up in abusive or neglectful homes display behaviors that are very adult-like or disturbing given their young ages. And the children themselves are often very surprised when another child or adult points out that such behavior is odd and abnormal.
Troubling unchildlike behavior is often a major indicator to psychologists, teachers, and healthcare professionals that a child may be living in an abusive/neglectful home or environment.
One of the regular, rather young trolls of True Capitalist named "Asho" has had a habit of doing this repeatedly, though thankfully not to serial killer levels; this has actually turned him into The Scrappy for a lot of people, even those who hate Ghost. He once called Ghost while high (and slagged off his mother while doing so), and another time called Ghost while drinking illegally and watching porn; the latter incident, he called back the very same show, while masturbating. He claims to be younger than ten.
Examples of kids trying out such troubling behavior for the first time:
Anime / Manga
One Piece showed Sanji started his smoking habit at age nine trying to be more adult.
A little later, but in Ichigo Mashimaro, Nobue started trying to smoke in middle school. It nauseated her when she first tried it, but she "powered through" until it didn't make her sick anymore, and now she's addicted. What started it all, however, is when a smoker left a pack behind on a park bench when Nobue was 11. Curious, she picked it up and looked at it. The warning label scared her off of starting for a while, although she did start holding a cigarette in her hand in an attempt to look cool.
In Belgian comic Violine, the titular 10-year-old drinks whiskey and gets clearly drunk off it, when it's given to her as part of a celebration held by friendly natives in an African country.
In Chapter 14 of the Superjail! fanfic Extended Stay, the Warden and the Mistress, after getting worked up over their 4-year-old twins Matilda and Ethan running off, finally find them beating and whipping the inmates alongside Jailbot, NOVA, Alice and Bruce. Oddly enough, Warden convinces his wife that this means they are good parents and they actually decide to help their children beat the crap out of their victims.
Although to be fair, the parents in this case are prison wardens who take pleasure in straight-up torturing and murdering their prisoners, so it'd actually be no surprise the children would pick up on that.
Again in Hounddog, Lewellen is tricked into doing a naked dance for a much older man for Elvis tickets and gets raped because of it. This carried over into Real Life, where many people were shocked that 12-year-old Dakota Fanning had played such a scene herself.
O-Ren Ishii of Kill Bill commits her first murder at the age of eleven, an incredibly bloody revenge upon Boss Matsumoto, who just two years earlier murdered both of her parents with the help of his men. And the reason that O-Ren was able to get close enough to Matsumoto to kill him? Matsumoto was a pedophile.
A mailman is making his rounds, but one of his deliveries is a package that requires a signature. So he goes up to the house, knocks on the door, and a 12-year-old kid with a cigarette in one hand and a glass of scotch in the other answers it:
In Freak the Mighty's sequel story, a girl nicknamed "Worm" ends up hitchhiking with the titular character of the sequel. And he promised his grandmother that he wouldn't do that.
In the classic children's book Nothing's Fair in Fifth Grade, one of the main character's friends decides to hitchhike a ride to a local fair, as she's tired of walking. The rest of the kids are shocked, but go along so as not to get left behind. The hitchhiking adventure ends up having disastrous consequences for the kids. The man drives off away from their intended destination, and the kids jump out of his truck at a red light. But one of them, a 7-year-old, goes back for her purse which she forgot, and the truck drives off with her in it. Looking for a phone so they can call the police, the kids head towards the nearest building they can find: a tavern. Suffice to say everyone in the tavern finds the procession of fifth-graders and the one girl's 3-year-old brother to be a rather strange sight.
In the novel Others See Us the protagonists are quite startled when their grandmother insists they have a beer. Though it's actually a trick to increase their psychic powers.
In the Judy Blume children's novel Then Again Maybe I Won't, main character Tony, his rich next door friend Joel and his old friend from the inner city, Frankie, are hanging out in Joel's basement when Joel jimmies into his father's liquor cabinet. The three boys get drunk. It was the first time Tony and Frankie had done this, but Joel had been drinking enough that he knew well the differences between the various kinds of alcohol.
In His Dark Materials, mention is made of Lyra and Rojer sneaking into Jordan College's wine cellar and trying "the oldest, twistiest bottle they could find". They both end up vomiting all over the place. Rojer questions the sanity of adults who enjoy drinking the stuff, while Lyra stubbornly declares that she likes it.
Palpatine's youth was chronicled in Darth Plagueis, and he was mentioned to have done enough delinquent stuff to have had his butt thrown in a reform facility had his father not paid off the authorities to if not let him get away with his crimes, then certainly lessen the punishment to be significantly less than it should be (eg, expulsion).
Live Action TV
The Malcolm in the Middle episode "Lois Battles Jamie", there are two instances of this subtrope occurring. The first was Jamie trying to murder his mother by dropping a shelf on her (although it's subverted in that he's acting like this because his brother Reese fed him soda, which evidentially made himself uncontrollable). The second was with Francis in a flashback. When he was a toddler, Francis attempted to douse his teddy bear with lighter fluid and set it on fire (similar to certain people who kidnap other people) before Lois intervened.
Rome has Octavian, no older than his early teens, who calmly tortures a man to death at the instigation of an adult. Another adult takes him to a prostitute, and his older sister seduces him. He combines this trope with Wise Beyond Their Years, which makes him even more unnerving.
The torture scene is particularly telling, since Octavian actually seems more comfortable with it than the battle-hardened veteran he's working with, openly explaining to the victim that they're going to kill him either way, and telling them what they want to know will make it easier. When the victim still refuses, Octavian suggests cutting off his thumbs as a good way to get started.
When we first see Mordred in Merlin, he's a normal child, albeit telepathic. Then the next time we see him, his camp gets attacked and several knights are about to take him back to Uther, who has drowned children in the past. He kills them. It's justified, but afterwards he just gives a small satisfied smile. Keep in mind this kid is 9 or younger, and has been raised by Gandhi-level pacifists.
From "Little Kids" by Deerhunter:
kids drinking gin on the front lawn the kids see that man walking down the dirt road these kids see the sky and they think of him dressed in flames kids walk behind, slowly stalk, that old man
these kids followed him to his shed where he turns on the radio and smokes a cig these kids come with gasoline and they strike a match
Day of the Barney has Barney convince his fans, who are all young children, to kill any adult they can manage to. Specifically featured are two children offing their mother.
In the Futurama episode "Bender Should Not Be Allowed on TV", Dwight and Cubert take up smoking, robbery, and other activities to emulate Bender. It's played for laughs, and there are no dire consequences, but the kids do projectile vomit after smoking. Even better, their accomplice in this is Tinny Tim. The robbery is his idea: "Gentle jerkwads! I know of a way we can emulate Bender without throwing up!" Best part: Tim's a robot, so alcohol shouldn't, logically, make him throw up anyway, because he runs on it, so this falls purely under Rule of Funny.
In Ben 10, Ben meets Kevin 11, an eleven year old boy who gambles and steals things. This is troubling enough, but Ben still thinks Kevin's a cool guy to hang out with...until Kevin is willing to use his energy absorbing powers to crash two subway trains together and take the cash from the wreckage. When Ben points out that "hundreds of people could DIE!", Kevin shrugs and says "Hey; no pain, no gain."
Eggy the duckling in The Penguins of Madagascar absorbed the knowledge of all four of the penguin squad while still in his egg and became a Tyke Bomb obsessed with the commando life. His mother wasn't pleased.
Shapey (and eventually Block) are shown playing with things like lighters and drills in Moral Orel which Bloberta and Clay don't keep these things out of reach.
Kevin from Kevin Spencer, who's age throughout the series ranged from 14-17. Kevin has engaged in arson, theft, drinking, smoking, attempted murder, and several other crimes. His life pre-series was bad enough to get him into a correctional facility for the first season.
According to The Encyclopedia Of Serial Killers, 10% of serial killers make their first kill before the age of 10. And even if they haven't killed anyone just yet, there are often signs that something is not right about the child. Torturing animals and sadism are two common signs.
An odd example is the case of Ted Bundy, one of America's most notorious serial killers. Although he didn't kill anyone (that we know of) in his childhood, there was that time when his aunt woke up to find her bedspread covered in knivesand little Teddy sitting beside the bed, smiling up at her...
Mary Bell made her second at the age of 11, making her the youngest serial killer in history.
About a dozen twelve year old religious Israeli girls in Hebron (town in the West Bank) decided to go into the Palestinian section of town one day and start harassing vendors in the market. The three Israeli soldiers on the scene (who lacked the power to arrest Israeli citizens) could not even touch the covered arms of the girls since the soldiers were all men (there's a religious taboo), and if the Palestinians had fought back, the soldiers might have had to arrest them, even knowing how ridiculous the situation was! Since police never came, all the outnumbered soldiers could do was try to stand between the girls and the vendors. Clearly, the girls had planned ahead and realized what they would be able to get away with considering the division between army and civilian control. This incident was not repeated.