In DC's 52 (not the new 52, but the year-long weekly series that followed Infinite Crisis), a member of Lex Luthor's private super-team was clearly shooting up heroin, but the word heroin was never used. She was always just described as being "on the sharp," and then "off the sharp" when she stopped using. Any readers not familiar with drug slang might very well have missed exactly what was being referenced, although this is a borderline example, since the illustrations clearly showed her shooting up something.
In an Adventure Comics Sandman story in the 40's during The Golden Age of Comic Books , there is a picture on a wall in the background of a nude woman.
That book spun off a DCAU style Harley & Ivy miniseries, in which Harley Quinn and Poison Ivy wash each other's hair in the prison shower and sleep in the same bed once they break out. Word of Gay has said it was exactly what it looked like.
There is significantly more going on in Harley and Ivy than hair-braiding, but all that need be noted is that Harley alternates between an abusive relationship with the Joker, and a caring and slightly less abusive one with Ivy. Notice Harley's wording too. A "special shot" so they "won't get sick" (Ivy is a Poisonous Person) from 'playing'?
That is to say nothing of the subtext about Barbara and Kara that makes it clear as water. (You'll notice that Batgirl doesn't actually deny it.)
Furthermore, there's a part in the first collected edition of the New 52 Harley Quinn ongoing series where, out of the blue, Harley asks Ivy if she wants to see Harley's beaver. Only mildly surprised, Ivy says she does... only to find out that it's an actual stuffed beaver.
There's a short Batman written by Brian K. Vaughn which has the Joker or rather an impersonator breaking into a factory and rearranging the chemicals to spell dirty words. For example, boron, argon, and fluoride become B-Ar-F. Then he mentions he also did copper and niton.
The Brave and the Bold: Issue #197, "The Autobiography of Bruce Wayne", has an image of a shoebox that says "Pedophile", meant as a pun for a foot lover. The artist admitted it was tacky, and it was removed from the collection "The Greatest Batman Stories Ever Told".
In Impulse, thought balloons frequently had pictures representing the character's thoughts. At one point, Max Mercury responded to an unpleasant surprise with a picture of a dam.
Impulse took this habit with him into Young Justice. Once, when Wonder Girl was nagging him, his thought balloon contained a picture of her as a dog.
The crossover arc Sins Of Youth had an aged down Aquaman informing Stargirl that he could hold his breath indefinitely. For bonus points consider that while physically Aquaman was a child and Stargirl an adult at the time give or take some magic based confusion mentally the opposite was true.
Invoked in one of the artists' sequences in Issue 0, which Conner shuts down because it wouldn't make it past editorial, and played straight for the title of Issue 7.
Harley appears to say some serious profanity after her tooth is knocked out by a brutish roller derby opponent. However, it sneaks past since she's taking it out of her mouth while saying it, rendering the profanity as the garbled, "mygluggin'toooph!"
In a flashback Satanna can be seen wearing a shirt that reads "CU Next Tues".
Karen says to a potential employee that was playing with her snow globes to "Please, stop messing with my globes." The visual joke is evident◊. To really hammer it in, the next panel has the guy say "sorry, force of habit."
From an issue of Titans in which Dick "Nightwing" Grayson insists the original members have to maintain their secret identities in front of the new kids, which means full costumes and codenames to hang out and watch TV:
Arsenal: Nightwing, you can be such a... Flash: No real names, remember?
In The Just #1, when Damian Wayne complains that his father and the other past heroes did their jobs too well, Alexis Luthor responds "'This Be the Verse'. Best poem ever." It's a Philip Larkin poem whose famous first line is "They fuck you up, your mum and dad."
In a Superman story published within a month after Reign of the Supermen ended, just after rescuing "Clark Kent"note actually "Matrix" Supergirl in disguise helping him provide a cover story for his alter ego's absence and return from a rubble-blocked emergency shelter, Superman is nagged by Lex Luthor, Jr.note a clone with the original's brain posing as his own son about Supergirl's absence. Supes politely but firmly reminds him that Supergirl is her own person and what she does is her own business. Under his breath, Luthor calls him a "sanctimonious berk". In Cockney Rhyming Slang, "berk" means, well...
For a time in the '70s, Captain America was the target of a smear campaign by the Committee to Regain America's Principles.
In the series Civil War the Thing takes a sabbatical in Paris, and of course ends up fighting alongside a French superhero team. He celebrates his new allegiance with the warcry "Il est temps de battre!" (Strictly, it should be "C'est l'heure de se battre," but this is Ben Grimm.) In the next fight scene he gets a little confused and yells "Il est temps de foutre!" and the sexy superheroine alongside asks if that was exactly what he meant. Well she may, since the English word would only appear in a comic with stars after the F, and probably not even then.
Marvel didn't publish six issues of Giant-Size Man-Thing by accident. Deadpool actually made a joke about this once.
Along those same lines, Steve Gerber snuck "Phelch" (the name of a "space turnip") into Howard the Duck. Gerber pretty much made a career out of getting crap past the radar; in Howard the Duck's first issue, Howard says that a large nest "reminds me of where I was first laid" (when reprinted in a Marvel Treasury Edition, the line was changed to "...where I was first hatched"). From all appearances, Gerber may also have been the first writer in mainstream newsstand comics to use "freaking" as a euphemism for "fucking."
The New Avengers are just learning of a new, villainous Avengers team. Carol leans forward to better look at the screen. Bucky... likes what he sees◊.
In an issue of New Mutants the characters go to Hell and fight demons who speak a seemingly nonsensical language. It is, however, translated at one point. If you follow each letter precisely, you can actually find the demons saying things like, "Fuck nuts" and "Hey dick-breath".
In Runaways, Nico says something about criminals filling the power vacuum left in L.A. when their supervillain parents died, and Chase suggests that "power vacuum" should be Gert's codename. Gert is Chase's girlfriend. Eleven-year-old Molly gets it; apparently, the censors didn't.
One of the most impressive examples of this is in The Sensational She-Hulk graphic novel, where in one specific panel where the titular character is wearing a shredded top after getting shot at by several soldiers, and her nipples are clearly visible,◊ barely covered by what's left of the shirt. The inker revealed that he added them in without John Byrne's approval and that deadline crunch was most likely the reason they weren't caught.
In Amazing Spider-Man #598, Spidey infiltrates the Dark Avengers using a special Venom disguise. Unfortunately, he is captured and Bullseye tortures him (with a high tech device meant to simulate drowning) to get the password necessary to remove his mask. After quite a bit of torture, Spidey tells Bullseye that the password is "Bowl...Psi...Isad...Oosh. You say it all together." (In case you didn't get it: "Bullseye is a douche.")
In the Colleen Coover story in the King-Size Spider-Man Summer Special, the Enchantress calls for her laptop computer. "Why?" asks one of her henchthings. "The usual. To look at ladies." (It's part of a diabolical scheme, but given the givens...)
People tend to forget it since it was the issue Venom debuted in, but at one point in the story, Mary Jane actually allows Peter to take some nudie pictures of her. As if that weren't enough, the caption for the scene says "Peter's spirits begin to rise." Seen here◊.
The Tomb of Dracula character Hannibal King has uttered some lines that suggest that he may be gay or bisexual. When rescuing Blade from death, he said: "He may hate my guts 'cause I'm a stinkin' vampire, but he's dynamite to work with." And after subduing one of Deacon Frost's minions, his threat that the guy complies or else ends with "Understand, sweetie?" One could argue that it was The '70s and there was quite a lot of gender-bending dialogue. Luke Cage also called male and female alike "Sweethart". However, in The '90sTOD followup Nightstalkers, King's response to Blade's empty threats is "Smooches! Love you too, big guy". In a 1998 Blade one shot, Blade explains in narration that he has to go get King "out of the closet". Quite a double entendre, even though we know that King was sleeping in the closet in Blade's hotel room (to avoid the sunlight of day). Interestingly enough, in Blade: Trinity, Ryan Reynolds plays King as quite decidedly camp.
ThisWolverine cover. Kurt's obvious nudity aside, note both Wolverine's eyeline and the placement of the beer bottle. And it was intentional too, and to quote Greg Rucka, who once asked artist Esad Ribic about it:
Esad is a big, cheerful, man with a wicked sense of humor. He just looked at me. And then he smiled. And the smile got bigger. And bigger. And he said, And nobody at Marvel noticed! And then he couldnt stop laughing.
In the first issue of Young Avengers Children's Crusade, Billy and Teddy (canon boyfriends) are given a room at the Avengers' mansion which is a bare cell with twin beds. Teddy complains about the twin beds, so Billy uses his magic to redecorate the room to resemble a hotel room, complete with changing the twin beds into a nice queen-sized bed with mints on a pillows! Teddy and Billy then begin to comfort one another and are about to kiss, when they are interrupted by Tommy coming to rescue them. It's clear that had they gone on uninterrupted, they wouldn't have stopped at a kiss...
In the original X-MenDark Phoenix Saga, one of the first hints you have that Phoenix was really getting off from using her enormous power was subtly slipped in by artist John Byrne. During her duel with The White Queen, judging from her chestal region, she was either really turned on or it was really cold in Chicago that night. And since they had already established a few issues earlier she didn't even feel the cold anymore, well...
In X-Factor, Jean buys a white fur coat to replace her old winter coat. She and Scott are acting frisky, and are making vague, but not subtle comments about how wonderful the coat feels. Also, Jean is sensually petting the fur in one panel, and then has her arms intimately wrapped around Scott the next. These indicate, while still being family friendly, that they might have been planning on making love while Jean wore the coat.
Minerva Mink's boss: Miss Yum-Yum, is this year's model more robust?
The Entire Page sounds like they're describing some new-fangled sex gadget.
Asterix does this a lot, in typically French fashion.
For instance, in Asterix and Son, Asterix has had a baby abandoned on his doorstep. The Gauls disgustedly remark that it's unusual that someone would leave a baby with an unmarried warrior rather than a temple, and when Asterix asks what that implies, we see the judgemental expressions of every character in the room in separate panels until Asterix insists it isn't like that.
There was actually more of this added in the (UK) English translation than existed in the original work, thanks to the extremely relaxed British attitude towards Parental Bonus. The translator Anthea Bell says she thought at first she went too far in renaming the druid Panoramix (who supplies magic Super Serum to his fellow villagers) "Getafix", and came up with an alternate explanation for if the publishers or children pressed her about it (the idea that stone circles were used by druids to 'get a fix' on the stars).
He literally says the phrase 'get a fix on the stars' in Asterix and the Picts, in reference to this.
"Panoramix" in the original subtly suggests expansion of vision, as of the kind which might be created by certain substances. This is just a gag about psychedelic culture until The Big Fight, which he spends giggling at mundane things, enjoying even horrible music, and using magic to make things change color and float. The Animated Adaptation of this story uses him for some of the most Deranged Animation ever. His reputation is such that his image not uncommonly graces French tabs of acid, much the same as the use of the Pink Elephants from Dumbo.
The Romans have orgies. Several throwaway gags are made about this, but at one point there is an actual depiction of a Roman orgy which goes on for a page and a half and manages to imply all kinds of decadent sexuality without showing any nudity at all (it's mostly about eating disgusting foods). It does, however, show some pretty explicit clothes-on BDSM play - a Roman woman in the background is riding an old man around, lashing him with a whip and forcing him to eat with his mouth like an animal.
In one story, Asterix, Obelix, Vitalstatistix, and Impedimenta are returning from a meal, Obelix and Vitalstatistix both drunk. In the streets, they start having a loud argument. Obelix sides with Vitalstatistix, and they run at each other, hugging. At this point a man pokes his head out of a window above and tells them to 'take your girlfriend somewhere else, you decadent lot!'
In The Laurel Wreath Asterix and Obelix attempt to get themselves sold at a high-class slave market frequented by patricians. The slaves there include an effeminate, skimpy-clothed teenage male character who is obviously supposed to be a delicatus, an androgynous, adolescent Sex Slave kept by wealthy Romans in history.
Bravura, who had a weird kind of romance with Asterix in her story, imagines in Asterix and Obelix's Birthday him captured by a miniskirted, petite (but still One Head Taller) Gaulish warrior woman who has confiscated his magic potion and is tormenting him with it, his face contorted in sadomasochistic ecstasy.
Asterix and Obelix's Birthday mentions 'beatnix' who 'get nicely stoned at Nicae'.
In The Beano issue 3421 we see The Bash Street Kids' Headmaster's office. It is full of books with head related titles eg Being the Head, Head Stuff and Heading. We also see another book with it's title which is partially obscured but the words Giving 'ead are clearly visible.
After many years of trying to write realistic language in comics, only to have the editors change words like "dick" to "dork" and to cut references to masturbation entirely, Neil Gaiman finally scored in The Books of Magic. In his original script, John Constantine says "Fucking hell" (and the circumstances fairly justify strong language). The editor refused to accept that, and Gaiman changed it to "Felching heck", which the editor apparently assumed was some kind of bowdlerisation (it's not: it's far stronger than the original phrase) and let it go to print.
In one of the Blue King City of Heroes comics (specifically the first Dread Carnivale), in the second nightclub scene there's very clearly (if you know where to look) a woman, dancing entirely naked. Possibly an oblique reference to the Game Mod which allowed you to do just that.
A lot of the 70s series of Conan the Barbarian featured instances of getting past the comics code. One issue features man-eating flowers (It Makes Sense in Context), and the flowers start out white, but as someone falls into them, they slowly turn red. Another has Red Sonja noting Conan's wall-climbing abilities, and wonders if the other tall tales about Cimmerians are true. As she's looking up at him, and he's basically wearing a loincloth...
During CrossGen's first run, Obregon Kaine's Catchphrase in Negation is BOHICA, the literal meaning of which ("Bend Over, Here It Comes Again") he explains upon request. Compared to the rest of the Sigil-verse, where anything stronger than the odd "damn" is heavily censored...
Another Donald Duck story titled "It's A Dog's Life" have Magica DeSpell catch wind of Scrooge planning on getting a dog to guard his money. Using that as an attempt to steal his no. 1 dime, she transforms herself into a dog and tells the camera: "There! You may call me a bitch now, if you like!"
In one issue of G. I. Joe: Special Missions had a sniper taking out mines that Cobra aircraft were dropping along the course of a tanker that the Joes were escorting. After having quite a bit of difficulty lining up a shot on the final mine, the sniper's next words are "Got you, you son of a-". The following panel has the mine exploding with the sound effect BITCHOOOOM!
In the Muppet comics, it was revealed just how adult Floyd and Janice were. In one comic that explored the question "Just what is Gonzo?" Floyd answered with "Man, he can swing any way he wants. That's cool." In the comic spoofing Robin Hood, Janice plays a character named Willa Scarlet who is an expert on herbs.
Flax Seed even keeps forgetting what he was going to say and is convinced that Filthy Rich's billboard portrait is always watching him. On top of that, he stares at the sky at random moments and stays like that with a vacant expression.
The party after Rarity's fashion show included ponies gambling and blatantly drunk (especially Rainbow Dash) plus Sweetcream Scoops is making passes at Big McIntosh while two stallions are trying to seduce (a very uncomfortable) Fluttershy.
Pinkie Pie is peeking into the stallions dressing room with Rainbow Dash on the first page while Fluttershy watches in something between horror and embarrassment.
British comic strip School Belle, which was part of the Buster weekly, had one story where the titular Belle was playing snooker. The boys at the club start taking bets on colours, which Belle takes to be which ball she hits first. Too late, she realises that they're actually waiting for her to bend over so they can see what colour her underwear is.
Sergio Aragonés likes to sneak penises and bare-breasted women into some of his background scenes, particularly Groo the Wanderer. Given the cartoonish style of his work, it's more comedic than titillating.
Ninjara: Just me and my two Raphs. What could be better?
Future Raphael: (Thinking) Another Ninjara.
Young Raphael: (Thinking) Some whipped cream.
Tintin: In 1934 Hergé drew a story named The Blue Lotus in which Tintin travels to China. Hergé's friend, a Chinese foreign exchange student named Zhang Chong Ren told him a lot about Chinese culture and society, including the then current situation in Asia, where Japan had military occupied China. He also wrote all the Chinese signs, billboards, ideograms and texts seen in the backgrounds. As a Bilingual Bonus only Chinese people could read these. This also might explain why the book wasn't censored from the start because many of these texts are anti-Japanese slogans, like for instance: Boycot Japanese products, Abolish unfair treaties and Down with Imperialism. Upon realising the anti-Japanese tone of the story, Japan's diplomats stationed in Belgium issued an official complaint and threatened to take their complaint to the Permanent Court of International Justice at The Hague. Zhang congratulated Hergé, stating that it would only further expose the actions of Japan in China to further international scrutiny and would make Hergé "world-famous".
The adult comic Viz had an entire strip built around this. "Sweary Mary"'s appearances in the comic revolved around her efforts to get crap past the radar so she could swear as much as possible without being censored. In her last appearance she finally achieved her life's dream of being allowed to swear on the cover, but lost her voice and was ridiculed by the other characters.
The adventures of "Toni Gay" and her sometimes-boyfriend "Butch Dykeman". A late-50's comic that only appeared a few times as part of Archie-comics-style anthology collections. Believe it or not, there's even more innuendos than just their names- link for more info