Many fan fictions of children's cartoons tend to be much more violent than their source material.
It also happen with live action kid´s movies and television shows (Like for example, the infamous Agony In Pink, which despite being based on Mighty Morphin' Power Rangers, it was definitelyNOT for kids.
It works the other way, too. Some fan works of darker series can be much lighter than the source material, and in extreme cases, trick an unaware viewer into thinking it's family friendly.
SuperSaiyanKirby Adventures was known for being your standard Nickelodeon show, albeit fan-made. Then there's the sequel, which involves drinking, swearing, and so much more!
The original wasn't exactly the nicest either. Check out this episode that's directly based off of the mentioned "Cupcakes" fanfic.
The Bunker is a sitcom, and on the other hand there is this show, Which has banned episodes posted on another wiki.
The original contains subs.
Rocky Raccoon and the Forest Friends looks like a kid friendly anime. But is full of blood and gore, it is highly inspired by "Happy Tree Friends" but kids at age 10 still watch it anyway.
Due to Values Dissonance and an unusual inversion of Avoid The Dreaded G Rating, it's fairly common for online fanfiction to end up with what many would consider to be a hilariously inappropriately low rating in order to attract a greater audience. Archive Of Our Own in particular is notorious for this, hosting terrifyingly insane works such as Silver-furred Secrets.
Professional Wrestling
It's (partly) unintentional here. When it began to be touted as popular entertainment in about the 1940s, pro wrestling was family-friendly. The faces always did the right thing, the heels were evil But Not Too Evil, and moral ambiguity was never created. This pattern began to break down once "Arab" wrestlers such as The Sheik and Abdullah The Butcher began staging deliberately gory matches (the equivalent of "Hardcore" matches today) and the heel characters actually began to be depicted as Loveable Rogues and competent enough in the ring not to have to resort to cheating all the time. All bets were off once the "Attitude Era" got underway in the late '90s and sex and violence (and even the occasional dollop of Satanism) actually became the selling points - but parents still took their children to the shows!
In the late 2000s, WWE tried to steer itself back toward more family-friendly entertainment, due to John Cena's kid-friendly appeal, the Chris Benoit tragedy, and Linda McMahon's repeated failed political campaigns, but even that seems to be over now.
Religion
For people who only think of The Bible as only "Jesus and the Ten Commandments," they could be in for quite a shock. The Old Testament includes laws about slavery, and has stories of blood, gore, pre-meditated murder, incest, rape, and genocide. There's also the Song of Solomon, Ezekiel and his donkey penis metaphors (or perhaps just straight comparisons), and the entire story of Samson.
Classical Mythology is taught in classrooms. Granted, often it's a bare-bones, watered down version—but recounting stories like that of Aphrodite's birth (she was born from Ouranos' nads, which were chopped off by Cronos and thrown to the sea), or that Zeus and Hera were both brother and sister and husband and wife, has to be difficult to teachers of twelve-year-old students.
Tabletop Gaming
The hobbyist boardgaming industry runs in to this every which way, to the extent that some US publishers put notices like "THIS PRODUCT IS NOT A TOY, NOT INTENDED FOR USE OF PERSONS 12 YEARS OR YOUNGER" on titles containing heavier subject matter (example given from this—apparently the title didn't give it away, nor the face-eating aliens, brutally beweaponed killing machines, and human skull motifs on the cover). After all, board games are kids' stuff, right?
Bunnies And Burrows is a game based loosely on Watership Down and is chock full of cute little player controlled rabbits being brutally eaten by predators, ravaged by disease, and otherwise struggling to survive. Gamers thought it was for kids because it has talking rabbits, kids were disappointed when they found out there were no wizards slinging fireballs for 50,000 damage. It has, however, become a Cult Classic among those who understand this is not a kids game.
Rifts. Every book in the series has a stern warning at the very beginning the game is not for children and contains graphic violence and sexual references. Even so the publishers still get complaints from parents who think its family friendly like Dungeons & Dragons.
Theater
Avenue Q. Almost all the characters are Sesame Street-style puppets. Misguided adults might decide to take their children (despite the warning signs outside the theatre). Then the puppets curse and have sex and sing about porn.
Don't forget misguided adults taking their own misguided family-friendly selves along, too. Heard inside the theater lobby before the show: a poor souvenir vendor attempting to explain to an increasingly-shocked-and-disgusted adult patron what "Yeah, They're Real" referred to.
Actors performing in the UK tour regularly tweet about seeing very young children in the audience
"And although we're a low, hasty put-in show, the kiddies cheer on cue... Families come, if they're dumb, but then out they go, when our fuzzy people screw! Don't expect The Muppets, these are horny puppets, rated X on Avenue Q!"
One can also count Shakespeare in general. (However can classics be utterly filthy?)
Waiting For Godot is on some fifth-grade reading lists because the words aren't very complicated. Even though it makes no freaking sense even to adults. In a way, this is actually worse than showing kids something violent or sexual—how do you explain to a child that she got an F on her analysis of the play because she said it was about two people waiting for Godot?
They also discuss hanging themselves so they can get an erection. The only reason they don't is because the rope breaks.
At one point in its London run, The Phantom of the Opera sequel Love Never Dies offered free tickets to children. Beyond the fact that Phantom isn't kid-friendly to begin with, the sequel features the following: Alcoholism, stripping, infidelity which allegedly produced a child out of wedlock, a song with accidentally pedophilic undertones and murder.
Stephen Sondheim's Into The Woods. Oh, it's a cheery musical with all of our favorite fairy tale characters together! Then Act Two comes around, most of the characters get killed by a rampaging giant, and suddenly it's not so cheery anymore. The show has enjoyed myriad School Play productions anyway, but as of The New Tens the show's licenser now offers a "Junior" version for school and children's theater groups that drops the second act entirely (save for one song, "Children Will Listen").
The Four Seasons-themed (as in the band, not the Vivaldi piece) musical Jersey Boys would seem to be a wholesome, family-friendly musical considering how wholesome and family-friendly the music of the Four Seasons (and Frankie Valli) is, but is laden with profanities, double entendres, and very adult situations. This is why there's always a big sign posted in the lobbies of theaters showing Jersey Boys warning parents of the adult content present in the musical.
Playwright and poet Henrik Wergeland from Norway once wrote a short stage play on behalf of the Jewish cause. In this play, an eleven year old boy accidentally kills another (jewish) boy with a stone throw, and the (jewish) mother of the killed boy decides to help the under-age murderer in hiding from the cops, reasoning that he rather should be educated than put to death.
Ah yes, the play has been played by children for forty years, and it has even been stated that it is better off when the mother is played by a twelve year old girl. A play about murder and atonement, but hey, it`s culture.
Check out the reviews of Cirque du Soleil's Michael Jackson THE IMMORTAL World Tour at Ticketmaster.com and see how many parents say that the "Dangerous" number, featuring a bikini-clad acrobat (who used to perform in Cirque's adults-only production Zumanity) performing a daring pole dance, doesn't belong in a "family" show. The show is not marketed to families, but because of Cirque's name above the title and the allegedly family-friendly subject matter, oodles of them go anyway. Everyone seems to forget that Michael Jackson's work is a sterling example of What Do You Mean, It's for Kids? — full of adult themes and choreography from Thriller onward, and yet marketed to kids for years.
Toys
Subverted with Bandai's S.H. Figuarts line which is more geared towards adults even if most of the properties are based on children's shows such as Dragon Ball Z, Kamen Rider, and Super Sentai. With most figures hovering around 3,000-4,000 yen, the prices certainly would scare off some parents from getting these for their kids. Their most expensive figure Machine Itashar from Hikonin Sentai Akibaranger (which does fit under this trope) costs about 10 times what normal figures cost.
As mentioned multiples times here, any movie with the slightest potential for merchandising will probably have toys made for them. Often regardless of the film's actual rating.
Hot Toys figures definitely qualify under the above statement category although given their ultra realistic figures and hefty price tag, few would mistake these as children's toys.
Alien action figures: free Facehugger with each Alien!
It gets better. There's now Chest Bursterplush toys. Yes, cute cuddly plushies of an alien fetus that violently erupts from one's chest causing horrible death.
Plush toys, like animation, are not always for kids. Here you can find the ebola virus, the black death, gonorrhea, and salmonella for your kids to cuddle with.
Diseases, hell. You can get plush Eldritch Abominations.
Hey! My five year old god-daughter adores her Plushthulu.
Behold, Mori Chack's Gloomy Bear. Cute pink bears with blood covered claws.
Blade Of The Immortal trading cards and figurines are also commonly found in the toy aisle in Japanese markets. It's a toy that comes with candy so it must be for kids, right?
They're all artworks in their own right too, so don't remove the wrappers!
Collector's action figures in general; after all, no parent in their right mind would get their child a Dr. Manhattan or Marcus Fenix action figure.
Numerous people on Amazon.com have the habit of complaining that the "High Grade" Godzilla figurines made by Bandai are "too small for children" or how they have to "put the figurines together with too many small parts that kids can lose" or something similar. Never mind the fact that said "High Grade" figurines are meant to be collectible figurines for G-Fans to, well, collect and put on display on shelves NOT for children to play with.
Three out of the four Terminator movies are R-rated, all are violent and scary ... yet it inspired Terminator Mini Mates.
Burger King's "Kids' Club" meals included toys based on the Twilight film New Moon . . . which was rated PG-13 and not aimed at younger kids at all.
Little kids like stuffed dolls, right? Behold, the Chuckydoll
Web Comics
Las Lindas is passable as a kiddy looking comic. Bright colors, animal people...and then you get to page 5...
Lackadaisy contains gorgeous art of furry cat people with often enormous and adorable kitty eyes (the author admits she was influenced by Disney films like Bambi as a child)- and they earn their keep by bootlegging, people-hacking, and general classy dirty-handedness. Even the cutest member of the cast turns out to be one of the craziest.
Several posters in the Giant In The Playground forums were offended by sexual content in a recent Order of the Stickcomic, on the grounds that "children read this comic." So, apparently it's okay for kids to watch stick figures kill each other in various brutal ways (including committing genocide), but masturbation jokes are just going too far. Never mind that anyone who's mature enough to realise it's a masturbation reference probably has first-hand experience of the activity.
The creators of Penny Arcade did a sketch about the possibility of children reading their work. Elsewhere, they mention being invited to a school to give a class on drawing — they went, and enjoyed it, but they made damn sure to cut the URL from the make-your-own-comic templates that they handed out.
Homestuck may seem innocuous- it's a webcomic about four kids playing a videogame, after all. But that's only if you overlook the frequent and creative usage of very foul language (Karkat Vantas is the best example of this), high violence, the repeated sexual references and jokes, and occasional mild nudity. Not to mention the abstruse subject matter, characters, and plot details.
Jix is about a blue furry alien, but has mild cussing and various comics filled with copious amounts of cartoony gore...and partial nudity from time to time from the human character.
A lot of parents seem to think that because it is a musical, Dr. Horrible's Sing-Along Blog is perfectly fine for small children. Considering that it's centered around a villain's Start of Darkness and it sports lyrics such as "It's a brand new day, and the sun is high / All the birds are singing that you're gonna die"...yeah. A lot of it probably goes over the kiddies' heads anyway (one would hope), but still...
Not to mention the "the hammer is my penis" line.
Felicia Day mentions in the commentary (not that one) a fan who wrote to tell her "my nine-year-old daughter loved you in this...until Act 3."
Doctor Steel's "The Dr. Steel Show" segments were formatted in the manner of a kids TV show, but his line of toys ("Buzzsaw Babies", "Rabies Babies", "Polly Pukes-A-Lot", etc.) are obviously not all that kid-friendly. Unless you have really warped kids.
He also had a song on one of his albums, ostensibly the theme song for a cartoon show, called "Smoky the Kid-Loving Trout".
"Teen idol" pop music is popular with ten-year old girls. Consider how many songs in that genre is about sex.
There are ten-year-old girls who are fans of the song "Do You Wanna Date My Avatar". You know, that song that's pretty much about cybersex.
To make it worse, YouTube uses the TV Parental Guidelines and Happy Tree Friends got a TV-Y rating, meaning it's allegedly suitable for even the smallest of children.
The YouTube copyright school is one of the few episodes actually alright for kids... trouble is, pretty much the entire series is on the site and saddled with that rating.
They had to put a FOR MATURE STARKIDS ONLY!!! label on Me and My Dick. Didn't stop some of their younger fans from watching it.
You'd think that since That Guy with the Glasses reviewers often review children and family films and entertainment that it'd be appropriate for children. You'd be wrong. Even Linkara (the "tamest" of them all) shows comics featuring gore, sexual innuendo, drug use, and fanservice (though to be fair, he is criticizing these scenes).
On an August 2011 edition of his Radio Dead Air Internet radio program, TGWTG contributor Nash recounted the story of Pushing Up Roses receiving an angry letter from a parent which admonished her for using "foul language" in her videos because "children watch them". Nash was rather noticeably furious while recounting this, noting that That Guy with the Glasses is not a site for children (and that he hosts a show titled What The Fuck Is Wrong With You). The reaction from his stream's chat was similarly astounded and angry, especially because the letter was sent to Roses, who rarely uses profanity in her videos.
Many religious websites are family-friendly, although Jesus Is Savior is decidedly not. Designed to Scare 'Em Straight, grotesque imagery, anti-homosexual propaganda, Paranoia Fuel and surprisingly strong language for a religious site (Selena Gomez of all people is described as a "whore-brat") abound.
Mario Plush Forever, a plush series on Machinima. The name and the introduction of each episode makes it sound like it's just a kid friendly show, but you'll get to the first episode, which involves a curse that makes people have uncontrollable farts ... and turn into mindless demons! The first few episodes aren't too graphic, but once you get to Episode 10, things start getting graphic to the point where the director is putting a viewer discretion warning before each episode.
The original Making Fiends cartoons have shades of this. Ironically the series made in onto a Nickelodeon network, though even than it was dark compared to the others.
To a greater extent, Amy Winfrey's other work, Big Bunny. It has pets getting eaten, a zombie bluebird eating a girl's eyeball as she watches and inaudibly screams in horror, a squirrel hosting a Nasty Party and turning the remains of the victims into pies, use of the words "hell" and "bastard" (although in the literal sense), and a man getting his hand bit off by his left pocket. All with blood. Who knows how Making Fiends would have ended up if Nickelodeon hadn't stepped in at the middle of its first season.
Cracked has an article about a TBN children's cartoon that is about the Biblical story of Samson. It shows family-unfriendly things such as Samson chasing an old man into an alley and killing him (and you can hear his screams), singing a song about Samson basically committing arson, and saying that Samson enjoyed seeking pleasure from the ladies, then showing him at the home of a "lady of the night".
Other
Several stories on Not Always Right show that some parents believe "animation" automatically equals "suitable for children."
For everything said on the sister page about people in an adult Periphery Demographic who can't accept that some of the shows they like are for kids and will remain that way, it's worth noting that it cuts from both ends. You also have some Moral Guardians who see every show that isn't "kid-friendly" as an attack on children, rather than just for a different demographic.
A picture book for adults parodies "Goodnight Moon"-type children's books, and real parents' frustrations with children refusing to sleep; under the title "Go the Fuck to Sleep." (It's got cute illustrations of a mom and baby tiger.)
Even funnier is the story one Amazon reviewer tells: she bought this book, and in her absence her husband picked it up, thought it was a children's book, and read it to their little son, censoring out all the bad words. It's now their son's favorite bedtime book.
This example turned into a Subversion, though, when the author of Go the Fuck to Sleep released an amended version with all the bad words changed, so parents and little ones can enjoy it together.
Several Halloween costumes that little kids should not be wearing. Note: only costumes that can be bought in a store by a parent count. Handmade costumes do not count and neither do generic zombie or ax murderer costumes.
Freddy Krueger and Jason Voorhees. Hope the kid with the Jason costume doesn't role play with his mom who bought him it. *
Though if they did she would be the greatest mom ever.