Art Spiegelman's comment about his comic book Maus provides the current page quote. Maus features anthropomorphic animals as stand-ins for people (mice for Jews, cats for Germans, dogs for Americans, etc.). This does not mean it is kid-friendly. It's about the Holocaust. It features drawings of ditches filled with emaciated, dead anthropomorphic mice being burned by cats with flamethrowers and gas masks. The parts that take place in modern day aren't too clean either. Those parts deal with many serious themes like continuing racism, death in your family, abuse, and greed.
Stephen Desberg created a cutesy comic together with Stéphane Colman called Billy the Cat, which is about a teenage kid that gets transformed in a cute little yellow kitty. It features cute covers and equally cute friendly characters, but some of the comics (particularly issues 3, 5, 6 and 12) feature cats bleeding to death in alleys, a man getting impaled on one of his own statues, and a giant gorilla with a hook for a hand that kidnaps and harasses a little girl. The fact that a kid-friendly animated show was created based off the comic certainly wouldn't help matters much.
Stan Sakai, creator of Usagi Yojimbo, was asked at the Anthrocon 2005 panel Anthropomorphics in Mainstream Comics if he ever was told his comic was not funny and replied with the quote below:
For Usagi, yeah, at the beginning, you know, I'd get "Oh, cute and cuddly rabbit", and then they open the book and "... He kills people!"
The comic DID receive a Parents Choice Award (mainly for it's historically accurate depiction of life in Ancient Japan)
In 1985, United Feature Syndicate tabbed political cartoonist Jim Meddick to create a comic strip based on the Robotman And Friendsline of toys (and short-lived cartoon). Meddick took the original characters and settings for the original strips... and quickly abandoned them, turning the strip into an absurdist humor strip with decidedly not-kid-friendly storylines and dialog. Angry letters to editors followed. After about two decades, Meddick—at the request of UFS—wrote Robotman out of the strip permanently (he left Earth to be with his robot alien girlfriend) and rechristened the strip Monty.
Benoit Sokal's comics about a detective duck in a world of talking animals are decidedly not for children.
The original Teenage Mutant Ninja Turtles comics were definitely not child-friendly, being loaded with incredibly over-the-top violence and gore to parody the increasingly dark comics of the time. The problem, of course, is that the cartoon based on them was for children, and thus clueless parents could easily find themselves picking up an issue of the comic for a kid who was really into the Turtles…
#15 has a letter from a woman who complains that her son had bought a couple of issues which included "foul language and violence," without specifying any further, and that the company which "prints material for children" should know better. This was shortly after the cartoon started airing, but it's not mentioned at all in the letter. In his response, Peter Laird wonders what language and on-panel violence she's talking about (the foulest thing in the earlier issues being on the level of "let's go kick some ass!"), and points out that just because it's a comic doesn't mean that it's for children. Complaints like this led to the creation of the Archie series Teenage Mutant Ninja Turtles Adventures, which was based on the TV show and more kid-friendly.
Many people consider Spider-Man to be kids' stuff, but consider that some of the storylines in the comics would have to be heavily toned down for television—Spidey's got Serial Killers for villains, many characters dying or being murdered with often graphic results, brutal beatdowns, characters using or selling illegal drugs, and references to sex and rape.
Woe betide anyone who thinks that Batman's rogues gallery consists of only the colorful, largely Harmless Villains they saw on TV, along with the odd mobster or two. Many of the dozens of minor Bat-Villains from the comics (like Cornelius Stirk, Mr. Zsasz, and Jane Doe) haven't made it into the cartoons for a reason. Hell, even the ones that have been shown on television generally have at least one or two "absolutely under no conditions show to little kids" scenes in the comics. Exhibit A: victims of the Joker's Laughing Toxin when they've gotten a BIT too ripe.◊
Yes, this even applies to the likes of Penguin and Riddler. The former? Used a flame-throwing umbrella to burn the wooden masks of three of Black Mask's henchmen into their faces. The latter? While he was possessed by the demon Barbathos, gleefully stuffed a ping-pong ball down a baby's throat and forced Batman to remove it with nothing but a rusty knife.
In an interview in Amazing Heroes #119, writer Max Allan Collins said that, in reference to a Frank Miller written story which had Catwoman as a former prostitute, he found that inappropriate—the equivalent of doing Peter Pan and having them face historically accurate pirates. Collins felt that Catwoman was derived from children’s entertainment, appearing in a series that had turned into a much more overtly juvenile version of The Shadow (Catwoman debuted soon after the début of the Kid Sidekick with shaved legs, short shorts and elf shoes) and therefore people should keep that in mind when handling her.
Batman: The Animated Series is a dark and gritty series, but still considered family friendly. The Batman Adventures tie-in comic is considerably darker, has more blood and violence, and has references to sexuality. It's taken even further in the Harley and Ivy subseries, where hinting at the sex lives of the title characters is arguably a large part of the point. In one, the two characters in question are sleeping in the same bed at one point, and Harley says that she loves Ivy "more than Mista J" and Ivy makes several direct references to the Joker's physical and psychological abuse of Harley, which she (Ivy) is disgusted with.
We 3, by Grant Morrison, is about three talking animals trying to find their way home; the covers feature "missing pets" notices written in childlike style. Kids'll love it, right? Sure! Except for the scenes featuring the cybernetic animal soldiers literally tearing apart the soldiers meant to come kill them, the part where the rabbit explodes while hurling itself at a car, and all sorts of graphic violence in between. Oh, and it's being adapted into a movie directed by the guy who made Kung Fu Panda. Prepare for some traumatized children... As if the Vertigo label wasn't a warning already...
Swedish comic strips Arne Anka and Rocky are filled to the brim with funny animals. They're also filled with alcohol consumption, sex and deep, deep cynicism. Luckily, Swedes are generally smart enough to check the contents of such material before handing it to their kids.
Somehow, the first six issues of Jeff Smith's Bone were excerpted in issues of Disney Adventures. Needless to say, it suffered some Bowdlerization (including two whole scenes getting cut out and all mentions of "God" and "beer" being changed to "Gosh" and "soda"). Most bookstores carry it, especially the colorized version, in the children's section instead of the Graphic Novels/Comics area. The fact that it was published by scholastic doesn't help either.
Frankly, danged near any mainstream Super Hero comic produced during the Darker and EdgierDark Age that ran from about 1988-1996. Between the ever-increasing levels of Gorn and the constant big damn universe-changing events, the two biggest comic companies are still throwing as thick and fast as they can, the only Marvel and DC comics even remotely meant for kids these days are the Adventures and Johnny DC lines. It's gotten to the point that pasting "HEY, KIDS! COMICS!" over hyped up and massively nasty pages has become a wide-ranging Internet meme.
It has been speculated that reason Batwoman (who was supposed to have her own series as far back as 2005) was kept on ice for so long is because WB execs were worried about upsetting parents by introducing a lesbian Bat-character in the wake of Batman's resurgence in mainstream popularity after the release of Batman Begins.
Played with in an issue of JLA: a woman receives a book of fairy tales from a recently deceased relative's estate, and decides to read one to her young daughter. She soon realizes that these are old school fairy tales involving cannibalism, mutilation, vampirism, and murder. Oh, also: the fairy tales are alive.
Whistles, a graphic novel by Andrew Hussie of MS Paint Adventures fame, was once listed in the Children's category on Amazon. Well, it's a comic drawn in a cartoony style about a funny clown, so it must be for kids, right? To quote the summary: "Whistles, a clown in the Starlight Calliope circus, was beloved by all. One day an accident nearly cost him his life, and he became exposed to the corrupt underworld of the circus, rife with murder and cannibalism. Forced to flee, he experiences the hardships of the world such as homesickness and prostitution."
Fables is a comic series about a whole community of fairy tale heroes who live in New York and their lives and adventures. The kids are gonna love it, right? Some of those adventures include: A murder mystery with an apartment drenched in blood, Snow White being raped by 7 dwarfs in the past, the nice, friendly and charming Boy Blue going on a trip to murder the Adversary and slaughtering anyone who gets in his way, a war and so on.
The Comic Book Legal Defense Fund is a fund that takes on the cases of comic store owners who they believe are wrongfully sued and/or arrested for which comics they distribute. Its two most famous cases are the Gordon Lee case (where he distributed a copy of a comic with nude drawings of Picasso on Free Comic Book Day) and Jesus Castillo (who sold an adult comic book, clearly labeled adult, and featured in the adult section of the store, to an adult, who turned out to be an undercover cop and arrested him for two counts of obscenity.) An excerpt from a prosecutor's speech in the Castillo case that perfectly summarises this trope:
I don’t care what type of evidence or what type of testimony is out there; use your rationality; use your common sense. Comic books, traditionally what we think of, are for kids. This is in a store directly across from an elementary school and it is put in a medium, in a forum, to directly appeal to kids. That is why we are here, ladies and gentlemen. We’re here to get this off the shelf.
The Savage Dragon comic was not at all appropriate for children, but there was once a kid-friendly cartoon series based off of it (just like the aforementioned Teenage Mutant Ninja Turtles).
Steve Purcell gleefully subverted this with his original Sam & Max: Freelance Police comic books. With the expectation that cheerily illustrated funny animals would be purchased by and sold to minors, he often addressed kids across the Fourth Wall with encouragements to engage in dangerous or vandalistic acts. Fizzball is one example, a sport where a full can of soda or beer is shaken up to extreme levels and beaten around with a big stick — try it indoors, kids! He was not content to simply give bad role models, but to get in on the fun. These were then adapted into a show ostensibly for children that aired on Fox Kids.
Barbara Slate's Angel Love comic book series of the 1980s, having rather cute cartoonish artwork, yet dealing with serious topics such as drug abuse, abortion, critical illnesses, and incest. The lead character's roommate also goes on a blind date with a child. It doesn't help that the style of writing also clashes with the topics it is dealing with. The Angel Love Special which closes out the series was the only book to have a "For Mature Readers Only" warning on the cover.
Those who have seen Wendy Pini's ElfQuest comics (themselves not totally kid-friendly in spite of careful scenery censoring in certain scenes) need to take warning that one of her later works, a sci-fi retelling of Poe's Masque of the Red Death, is definitely not for kids, containing as it does fairly explicit homosexuality and very graphic death via a disease which causes uncontrollable bleeding and breakdown of all body cells.
Most incarnations of the GI Joe comic book are VERY different than the more well-remembered cartoon show. Characters (both the Joes AND Cobras) get Killed Off for Real, and many of the stories deal with real world Political issues (arms dealing, evil dictatorships, freedom fighters, political corruption,etc). Despite being based off of a toyline, the comic likely had an older audience in mind.