From the Mouths of Babes

"and she asks me

"hey what's 'friendship-with-benefits?'"

so I give the big brother response

"it's a physical relationship, without any commitment"

mind you, she's 11 and I don't want to get into much detail with my sis

anyway she was quiet for a moment

and then she goes

"ok so like f***buddies then?""

- qdb.us #64104

Isn't it cute when a kid knows more than you'd think? Isn't it even cuter when they know more than you'd think about something that you'd prefer no kid knew at all? Especially if the kid is too young to be in the Competence Zone. It's a pretty sure-fire way to get a laugh, especially if adults have spent the whole episode trying to keep the kid from finding something out, and the kid knew it all along.

To anyone young enough to understand or who can remember what it was like to be young, it's funny because the child shows a complete disregard for the unsaid treaty between children and adults: Kids can learn things as long as they pretend they haven't and don't ever mention it. It works on numerous levels.

This trope often isn't exploited in full on television, because if a child actor actually says the darndest things, the Moral Guardians will complain. Instead, they say mildly darnded things. Other media will exploit this more fully.

See also The Talk. For a more general example of kids talking outside of their expected age range, see Little Professor Dialog. If the kid is performing a song they know that wasn't... written for a kid to sing, then it's Age Inappropriate Art. Sub Trope of Troubling Unchildlike Behavior.

Advertising

 * Quaker Chewy Granola Bars used to be advertised as being able to stop children from saying the darndest things. One of their ads had a little boy walking up to a bride and informing her that his mother can't believe that she (the bride) wore white.
 * A popular Norwegian advertisement shows a mother awkwardly trying to explain to her son that his goldfish is tired and needs a vacation, cue the boy's sister showing up asking what's going on, the boy casually remarks "Doffen has died" and leaves the room.
 * An ad shows a child meeting his dad's boss, and after a moment saying "Daddy, his nose isn't brown."

Anime & Manga
"Vivio: Wait, does that mean Fate-mama... is a gigolo?
 * Much of the jokes in Crayon Shin Chan are of this type.
 * Though mostly in the American dub. In the original dubs, all kids but Shin-chan (And a bit of Nene, the preschool equivalent of a Covert Pervert) are perfectly innocent, and (especially in the manga) it's hinted that Shin-chan doesn't know what he's talking about most of the time.
 * Kirimi Nekozawa from Ouran High School Host Club. For some reason, her minders decided to read her shoujo manga, which leads her to say things like "There's debauchery going on here, isn't there?" In the manga, she goes so far as to call the Host Club a "reverse harem".
 * The Magical Girl Lyrical Nanoha Lyrical Almanac Gag Series in Megami Magazine uses this for a punchline in one comic as Vivio somehow misinterprets her Fate-mama's having her own place to return to as, well...

Fate: What!? No!"


 * The backstory for Gundam Wing's Duo Maxwell gives him a non-swearing example of this. During a conversation with the priest and nun who raised him, he says he doesn't believe in God, but he does believe in the God of Death, because as he puts it, "I've never seen any miracles, but I've seen lots and lots of dead people!" The nun admonishes him gentle, but the priest laughs and admits the boy has a point.
 * A regular source of humor in the Gag Dub of Ghost Stories.

Comic Books

 * Subverted in Runaways with Cute Bruiser Molly, twice:
 * In the very first story arc, Karolina drags Molly out of the room just as the Runaways are about to witness their parents making a human sacrifice. Later, when they are discussing it, she solemnly tells them that she knows exactly what they're talking about: S-E-X.
 * In the 1907 arc, when child bride Klara explains about her "marital duties," Karolina looks horrified and Molly says, "He makes you do chores?" Karolina then looks vaguely relieved that the idea of sex as marital duty has not yet reached Molly's precocious consciousness. But in the next issue Molly tells Klara that "It's not even a sin, it's illegal. There's TV shows where they catch guys even..." It's been previously established that Molly's apparent naivete is a pretense she keeps up so that others will keep their guard down around her. In this case, she may even have been trying to break the tension.
 * Used brutally when she was kidnapped by  who manages to call her out on her use of her young age as disarming mechanism and tells her to drop the act. She glares. And then she tells the the man   Damn... jut damn...
 * In Demon Knights, a young girl thanking Amazonian Beauty Exoristos for saving the village from dragons adds "But you dress like a tart."

Fan Fiction
"Duck Look, mommy, his pants are tighter than yours!"
 * In All You Need Is Love four-year-old Duck Sherlock Penber shares with his mother the following observation about Mello:

Film
"Mike: She got her period. Should make for an interesting honeymoon, huh?
 * Sam's little brother, Mike in Sixteen Candles, about his sister, Ginny, who's getting married:

His father: Where are you learning that stuff?

Mike: School.

His father: Good. Gettin' my money's worth."

"Annie as Hallie: I don't mean to be jerky when you're trying to be all mushy and everything, but I know what mystery my dad sees in you.
 * From Airplane!: "I take it black, like my men."
 * From the 1998 remake of The Parent Trap:

Meredith: You do?

Annie as Hallie: You're young and beautiful and sexy and, hey, the guy's only human. But if you ask me, marriage is supposed to be based on something more than just sex, right?"

"Mom: And the prince took the beautiful young girl in his arms and said, "will you marry me?" "Yes", she whispered, "I will be your princess".
 * For that matter, both the twins are quite eloquent for 11-year-olds throughout the movie. It's just that this is the only time adult subject matter gets this treatment.
 * Much of what Short Round says in Indiana Jones and The Temple of Doom. "Maybe he like... older women."
 * From Drop Dead Fred:

Young Elizabeth: Did they live happily ever after?

Mom: Of course, Elizabeth.

Young Elizabeth: How do you know?

Mom: Because she was a good little girl. If she had been naughty, the prince would have run away.

Young Elizabeth: What a pile of shit!"

""Hey, Linda! You're a bitch!"
 * From The Wedding Singer:

"He... he may have Tourette's Syndrome, we're looking into it...""

"Jason: What are you doing here?
 * From Lethal Weapon: "My Mama says policemen shoot black people!" Mel Gibson was laughing so hard in that scene.
 * Eric in Mystery Team Take this scene in a gentleman's club:

Eric: My mom works here.

Blank stares

Eric: What? It's better than shaking your shit on the street."


 * Inverted in Kick Ass when Big Daddy is stunned by daughter Mindy's birthday request for a cuddly, fluffy puppy and a Bratz movie star makeover Sasha. She then lets him in on the joke, amending her request to a Benchmade model 42 butterfly knife.
 * Darian to the Big Bad in The Last Boy Scout: "Eat shit, you fucking redneck!"

Literature

 * Sefalet's left-hand mouth says things no child should say in Dirge for Prester John. And she has no control over it.

Live Action TV
"Patti: I find Rickie a little confusing.
 * My So Called Life: When fifteen-year-old Angela begins hanging out with an effeminate Puerto Rican boy, her mother Patti objects. Danielle, who delivers the final line here, is Angela's nine-year-old sister:

Angela: Okay, so maybe he's bi. Who cares? His cousin can still drive.

Patti: What? He is what? Do you hear these terms she's throwing around? Bi?

Danielle: It means bisexual."


 * In the Leave It to Beaver TV series, Wally tries to upbraid his little brother for falling for a panhandler's story. When he calmly states that he knew perfectly well the panhandler was making it up, Eddie demands to know why Beaver gave him money. "Because nobody ever told me a story like that before."
 * In another episode Beaver asks Ward if he's a married man. Ward assures Beaver that he is. Beaver asks if June is a married woman. Ward assures Beaver that she is. Beaver asks Ward "Have you ever kissed any other married woman besides mom. Ward replies "Why Beaver! Why would you ask a question like that?" Beaver says "I'm just wondering." Ward says "Well, actually son, no." Beaver says "I guess you were scared to, huh?" Ward says "Yeah, that's as good a way as any to sum it up I guess." Beaver says "I guess a guy could into a lot of trouble doing that, huh? Ward looks off, daydreaming, and mumbles, "He sure could... uh, buh Beaver, I've got to finish this plug son, so you run off and play."
 * Done repeatedly on Two and A Half Men. Jake would hear or see something at his uncle Charlie's house that his father, Alan, didn't want him to be exposed to. Alan would then launch into some bizarre explanation in an attempt to protect Jake's "innocence". We then learn that Charlie and Jake were just messing with Alan and that Jake already knew what was going on.
 * Intentionally invoked by The Man Show, with a kid they hired as "The Man Show Boy", who would go around town saying things to people they wouldn't expect a kid to know.
 * In The Fresh Prince of Bel Air episode "Be My Baby Tonight", 13-year-old Ashley asks Will to tell her everything he knows about sex. He is appalled as she goes on to say that she knows all about eggs, sperm and fallopian tubes. He says, "Am I going to have to wash your mouth out with soap young lady?"
 * In the third season episode of Good Luck Charlie, Charlie managed to scare off all of Amy's baby shower guests after revealing her mother's true feelings towards the guests.

Magazine
"EGM: Who's that chick Mario is rescuing up there (in Donkey Kong)?
 * EGM had two articles where kids of the new millenium were asked to play games from before their time and interviewed on their opinions. The results were precious.

Brian: It's Princess Peach.

Kirk: It's a hooker.

Niko: She looks cut in half.

Tim: Oh wow -- she's one of those pole dancers."


 * As a sidenote, that's Pauline, not Peach.

Newspaper Comics

 * The comic strip Calvin and Hobbes did this frequently, as Calvin knew just enough about the adult world to get into trouble. In one strip, Calvin lectures his father that everybody must do their part for the economy; in other words, his allowance should be raised so there is more money in circulation. His father says, "I've got to stop leaving the Wall Street Journal lying around." Later strips used Calvin's incredibly-non-six-year-old worldview to make political or societal statements. Even more incredibly, he did it without ever becoming preachy or heavy-handed.
 * "Why would it be worth four dollars a minute to talk on the telephone to goofy ladies who wear their underwear on TV commercials?" "When were you watching that?!" "Um... It was on... uh... during my morning cartoons."
 * "Do you have any kids, Uncle Max?" "Heck, no, Calvin, I'm not even married." "Oh. What difference does that make?" "Kid watches a lot of TV, does he?"
 * For a seven-year old, Mafalda certainly knows a lot about politics.

Video Games

 * Persona 3 has a fun example. New Years day has the guys in the team admiring the girls in their kimonos. The resident cute little boy Ken asks if the girls are cold. When questioned why it's because Junpei says that they wear nothing underneath. Cue Yukari stomping on Junpei's foot and asking if he told Ken anything else. (This may be better in Portable when it's possible to have a romantic relationship with Ken)
 * Solatorobo contains a mild case. While Elh manages to confuse Red and Chocolate about, one of the orphans immediately . Red replies that it makes it easier to play, volunteering a flustered Elh for babysitting duty. Only question is, how exactly did the kid know that...?

Webcomics
""My mommy says you're a pagan representation designed to steal glory from Christ and I should tell you you're gonna burn in Hell forever. I want a Barbie.""
 * The Cyantian Chronicles: Tae, during a conversation with Kea. Tae and Kea together, at points. Kibi, who is smarter than many adults. Collin and Quinn, during Akaelae.
 * Ghastly's Ghastly Comic: Tentacoo wape!
 * Christine, Sonichu and Rosechu's daughter from Sonichu does this in the Christmas special whilst dressed as the Virgin Mary for a school play. "I am the Virgin Mary. That's my story, and I'm sticking to it."
 * By the way, she's a little kid. Although, most people who know about the author seem to think he has no idea what the line actually means.
 * Jay Naylor's Better Days often invokes this to deliver a moral so objectivist it would make Steve Ditko puke himself.
 * Something Positive: Jason has a very awkward time playing Santa.


 * This Xkcd strip, in which a child finds "Daddy's Sports Illustrated Swimsuit Issue" - and has seen so many inappropriate things on the internet that they're shocked that the girls have clothes on.
 * "Parents, talk to your kids about popup blockers."

Western Animation
""Let me know when those costumes get heavy, ladies!""
 * Early South Park was based almost entirely around this trope.
 * The movie focused heavily on this too, but later episodes it seems the adults have given up. (In the case of some, like Counselor Mackey and Randy Marsh, they have their own issues to deal with.)
 * Yakko, Wakko, and Dot. I mean Yakko's physically about 10 or 11, Wakko's physically 7 or 8, and Dot's physically 5 or 6. And yet, some of the things they say are a bit...

"Hugh: (Spit Take) Baby making is very... complicated, believe me.
 * This gem from The Adventures of Jimmy Neutron, which deconstructs the Fridge Logic of a 10-year-old genius with an extensive knowledge of human biology when Jimmy tells his parents that he wants a baby brother:

Jimmy: Dad, Dad, it's not complicated. Really, really, it's --

Hugh: You don't know --

Jimmy: It's basically conception, right?

Hugh: (Sticks fingers in ears and hums "la la la la")

Jimmy: ...then a nine month gestation period...

Hugh: La la la la...

Jimmy: ... and then you have...

Judy: Sweetie, a new baby just isn't in the cards right now.

Jimmy: But mom, if the glandular timeline--

Hugh: That's enough! OK! Ha ha, I want pie! Anyone else want pie? I want pie!"


 * From The Legend of Korra, seven year old Ikki sees nothing wrong with letting Asami know that her friend Korra is in love with her boyfriend.

Real Life
"So I sat him down and said, "Son, I know you already know a lot of things, so why don't you do this: why don't you tell me what you know, and I'll just fill in the blank spots." About 30 minutes later, I'm sitting there with a pen and a pad of paper, going, "You can DO that?!?""
 * 1960s-vintage Talk Show host Art Linkletter had a regular segment on his program House Party called "Kids Say The Darnedest Things" -- later spun off into a show itself -- in which he interviewed children to solicit these kinds of observations for their comedic value. (Of course, being the 1960s, they were -- generally -- a bit milder than today's version.)
 * Bill Cosby picked up this ball from 1998-2000, with the show Kids Say the Darndest Things, which has yielded at least one compilation book.
 * This from Not Always Right.
 * The Daily Mail, a Conservative British Newspaper, has a similar section among its letters page.
 * Bill Engvall says this about when he had to have The Talk with his son:


 * This video