Captain Planet and the Planeteers featured several episodes which were darker than the rest of the series as well as children's animation in general. Linka's cousin dies of a drug overdose in "Mind Pollution", a drive by shooting of a family is shown in "Utopia", "Formula For Hate" covers the topic of AIDS, a teacher and a friend of Gi gets shot in a gang shoot out in "Teers in the Hood" (and the episode also shows realistic images of victims of gang violence, including a dead child), Wheeler's friend is killed in "Talking Trash", and throughout the series, the deadly effects of pollution are shown.
Tom and Jerry short "Heavenly Puss" is a lot darker than most Tom and Jerry cartoons. Tom is killed trying to catch Jerry, and is told that if he wants to get into Cat Heaven, he has one hour to make amends with Jerry... otherwise, he'll be condemned to eternal torment by a demonic bulldog. Tom justmisses the deadline, and is literally dropped into Hell, where demon Spike dunks him in a cauldron of boiling water. Fortunately for Tom it was All Just a Dream, but it was still a harrowing experience for him, and probably the audience as well.
Regular Show is generally a bit more adult and risqué in its humour and situations than other Cartoon Network shows. It however does have two particularly dark stories:
For an episode based around a jolly and happy holiday, the Christmas Special turned out to be this. I mean usually presents disappear and people are sad or something along those lines. Quillgangets his hands on the present he created and wishes for the destruction of Christmas forever, which then causes bombs to be placed on anything Christmas-ish including snow. Thankfully we never see how powerful the bombs were but it's very likely they could do serious damage and had he succeeded it would've been the largest terror attack in history. This would've likely caused no one to want to celebrate a holiday that goes hand in hand for a global scale bombing.
Family Guy entered this territory more or less from the season 4. In the first few seasons were a kind of humor who remember much of The Simpsons (with more crudeness and mockery), and the characters themselves are sane. However, it was not until season 4, and more recent episodes, which adds up to the brim extremely sadistic and violent moments with people being gutted, torn in half, beheaded, etc. Watch any occasional episode of the first three Family Guy's seasons and then see recent episodes like the third episode of "Family Guy Presents: Laugh It Up, Fuzzball!" and the full episode "Screams of Silence: The Story of Brenda Q", there is a clear difference.
Other clearest examples to see how the series has become Darker and Edgier are the following: Bertram crosses the Moral Event Horizon by doing something not so comedic. He kills Leonardo da Vinci. Stewie's apparent ancestor which nearly destroyed the universe. Then Peter throws an unconscious Stewie under Lois' car wheel, and promptly has her run him over, and there was Evil Stewie, who committed one homicide, cut off Brian's tail, tries to choke Stewie with it, and later tries to strangle said dog with his collar. Seems like Family Guy is getting more seriously menacing antagonists, aren't they?
Not to mention in a deleted scene, Evil Stewie grinds his fist into a one-year old school bully's skull, then murders his parents. And this was shortly before the other homicide he committed.
Brian's hallucinogenic trip in the episode "Seahorse Seashell Party" is often regarded as the most disturbing and dark animation in the show.
The episode "Life Of Brian" is probably the darkest episode ever in the series. The episode in itself marks a total change in the whole series because Brian is briefly Killed Off for Real and really Played for Drama. Damn, this show seems like it becomes Darker and Edgier in every new season. The first episodes were Lighter and Softer compared to the most recent.
Adventure Time started off as a light-hearted children's show (albeit with a heavy dose of parental bonuses, subversive jokes, and black comedy). The show took a darker turn around the end of season 2, in which we are presented with a villain with absolutely no quirky or amusing characteristics whose only goal is to end all life. Since then, we've seen the show openly deal with issues like death, mental illness, Mind Rape, suicide, despair, and self-esteem. The show is in its 6th season-a far cry from the candy-colored jelly beans shouting "Algebraic!" in the pilot so many moons ago.
Seriously, compare the season 1 episode "Slumber Party Panic" to the season three episode "From Bad to Worse".
Even better, compare Season 1 episode "Ricardio the Heart Guy" to Season 4 episode "Lady & Peebles".
Regardless, there are still some lighthearted episodes, such as "Shh!" and "James II".
Speaking of Danny Phantom, while being perhaps one of the edgiest of Nicktoons, the TV movie, "The Ultimate Enemy", was the perhaps the darkest episode in the entire series, as well as one of the darkest moments in Nickelodeon history.
Isn't the concept of the show pretty damned dark, too? I mean, the hero is half-living, half DEAD. Let that sink in your mind for a moment...oh, and Vlad's plan to win Maddie over by murdering her husband is pretty dark for a children's show.
Usually, Hey Arnold! is a fairly light-hearted Slice of Life cartoon with the occasional moments of Getting Crap Past the Radar, but one episode called "On The Lam" was pretty dark as well as hilarious. It involves Harold, Sid, and Stinky believing to blowing up an old police station with a rocket and they bound and gag Arnold so that he wouldn't tell anybody.
Not to mention the infamous "Cheese Festival" episodes. They usually start in a lovey dovey valentine style, with Arnold going to the cheese festival with his love interest, and Helga doing whatever she can to ruin the date. No matter how hilarious the episode is, they always have the same, depressing, dark ending; Arnold doesn't get the girl and is friend zoned, while Helga is left completely alone at the festival without a lover or even a friend, giving off a very miserable face just before all the lights go out.
There are also the episodes addressing Arnold's parents ("Parents' Day" and "The Journal"). "Parents' Day" is just straight up sad for the most part, given the subject matter. "The Journal" does have its fair share of comedic moments, but the Foregone Conclusion that Miles and Stella will eventually go missing and be unable to properly raise their son makes the whole thing kind of sad. The two parter does end on an optimistic note given that Arnold finds a map detailing where his parents actually went. This was supposed to be a hook for the second series movie, which unfortunately never got made.
Warner Brothers attempted to make the classic Looney Tunes characters Darker and Edgier in the 2005 series Loonatics Unleashed, only to result in massive outcry against the idea, and an overhaul resulting in a strangely drawn cartoon that wasn't very much in the way of new or interesting. A retool for the second season attempted to add more references to the original Looney Tunes, with mixed results.
Legion of Super HeroesAnimated Adaptation started out fairly light in tone, but the second season features a future laid waste by an evil warlord, the replacement of the young Clark Kent version of Superman with a rather disagreeable clone called Superman X, an utterly destroyed New Metropolis, and the death of one of Triplicate Girl's selves. Dark and edgy enough? No? How about, Superman X says Brainiac 5's going to do something original-Brainiac-level nasty at some point in the future. The other episodes showed similar darker shades such as a murder conspiracy where Timber Wolf was convicted of patricide, the Legion brainwashing Chameleon Boy to infiltrate Imperiex's lair, a child who will be responsible for Imperiex's creation in the future being hunted down for that exact reason, Dream Girl being kidnapped and forced to use her precognitive powers to fight against the Legion by a group of terrorists. Ultimately, Brainiac 1 influences Brainiac 5 with More Than Mind Control, and Brainy brutally kills Imperiex onscreen, turns on the Legion, puts a crown of Kryptonite on Superman - not the clone, our Superman. He begins to digitize the entire universe, basically assimilating the Coluans to be his army. The LOSH finale is how Wham Episode is done. We get an Earn Your Happy Ending, though, when 5 is able to drive 1 out during a Journey to the Center of the Mind, and Superman X can go home right and the restoration of the time-stream brings the third Triplicate Girl back.
V4 LSH in the comic book version, as well as being an example of Running the Asylum, was notorious for this. It was even parodied in the Amalgam Comics Marvel/DC crossover.
It's not just making 'em a little older, either. With Alien Force and Ultimate Alien, villain motivations go from "steal the Omnitrix and kick puppies" to ethnic cleansing, civil war with Black and Grey Morality and no good guys, people dying and staying that way, and consequences go from "astonishingly, nobody got hurt" to "Anything goes behind a Gory Discretion Shot and people stay dead." The last half of Ultimate Alien takes it farthest, especially with the episode "Catch a Falling Star."note Today, on your favorite kids' cartoon: A murderous criminal better suited for CSI gets back-alley surgery to alter his face. The amount of blood the team found from that was apparently impressive. We find he killed the "surgeon" (that is, the veterinarian who owed him a favor) and anyone else who got in his way. His sidekick is an actress with a messed-up upbringing that lead to her becoming like the many Real Life "groupies" of criminals. He had in fact put her in a Sadistic ChoiceDeath Trap back when he'd been more of a "cartoon" villain than a dark villain; her affection for him is explicitly compared to Stockholm Syndrome.The new Omniverse series is scaling it back - it's not without its more serious episodes, but there's a distinct lack of genocide.
Or there wasn't, but it's not looking good for Upgrade's race after the Knight of Cerebus villain trio destroyed Galvan B. Headed up by one of the main makers of Transformers Animated, this series has something of a Cerebus Rollercoaster with dramatic episodes being more common little by little though the funny is never totally abandoned.
ReBoot pulled this off rather well in season 3 by showing two young characters suddenly grown up, adapting to the change in writing style, introducing new locations, and expanding the scope of the series.
This was the culmination of a transitional phase of the story begun during the Web World Wars when Bob was thrown into the Web and the previously one-shot virus attacks became a full-on assault. When Enzo was required to take the role of Guardian and lost in a game, losing his right eye in the process... that was when the Darker and Edgier tone was cemented.
Transformers Animated did similar, starting with the season three opener "Transwarped". Instead of the usual light-hearted action/humor, it explored the ethical implications of building a sentient but simple-minded superweapon, dealt with Ratchet's troubled past, involved far more visceral violence (albeit to robots) and brought several main characters close to death. As of "Where Is Thy Sting" one Autobot character's been killed off grotesquely and the leader of the Autobots is beaten into a coma with his own hammer. We never do see him wake up, by the way.Word of God says that had the series continued, he would have been revealed as having been killed.
Beast Wars itself saw this after the end of season 1, which featured the death of Optimus Primal. The first, episodic, often very campy season stands in contrast to the more mature, more serious later seasons. Anyone Can Die also goes into full effect, though naturally, Optimus does get resurrected into a new toy, er, body.
Speaking of Beast Wars, Transformers Animated has a habit of borrowing characters, ideas, or scenery from the earlier Transformers shows and modifying them for its own purposes. In Beast Wars Waspinator was the lovable hapless Butt Monkey who blew up many times but always pieced himself together without any obvious lasting effects. In Animated he's a gigantic, half-crazed techno-organic bent on bloody revenge upon Bumblebee for (accidentally) having him sent to the stockades under accusations of treachery. When he blows up, he's also seen piecing himself back together, but the effect is intensely creepier.
Transformers Prime is the darkest and edgiest Transformers cartoon thus far. There's far less comic relief; disease, brutality, and the undead are common thematic elements; and deaths are common (the Autobots are actually shown killing Decepticons). Heck, in the first episode a character is killed by Starscream rather violently and his death is mourned throughout the series. Whenever a character is killed, they don't come back and are only referenced.
The Powerpuff Girls underwent this slightly for the movie. It was edgier and more serious than the majority of the series — not that that's hard to accomplish.
The episode "Knock it Off" had them sell the formula Dick Hardly, a villain who, despite having no superpowers, was thought by most fans to be the worst villain they ever fought, even worse than Him. He was an unscrupulous and cruel man who used the stuff to started cranking out "EXTREME" Powerpuff Girls. He used more Chemical X and less of the other ingredients resulting in malformed girls, whom he abused or callously destroyed, and for no reason other than greed. Later when he wouldn't give up the Chemical X he drinks it and turned into a monster and nearly sucked the life out of the girls leaving them sickly green and covered in spots. The professor and their clones were just barely able to save them. It was little wonder that Dick was the only originally-human villain on the show who was Killed Off for Real.
The "Speed Demon" episode where the girls travel to a grim future where Ms. Bellum has turned into a Mayor-hat obsessed wretch because the Mayor had been killed, the teacher is so traumatized that she keeps repeating a Madness Mantra about the girls leaving, and the professor is a shallow shell of his former self, not even going into the list of people who blame them, having suffered possibly even worse things. And it's all caused by Him who has reduced the town to an apocalyptic wasteland and becoming a literal Satan himself.
In the episode Super Zeros, where the girls try to act like their favourite heroes, they poke fun at this trope. Buttercup at one point complains, "And we're not all dark and tormented!".
In 2003, John Kricfalusi made a revival of his cartoon The Ren & Stimpy Show, called Ren and Stimpy Adult Party Cartoon, to allow him more freedom on what he couldn't do previously on the show. It was darker, much more violent, the characters used stronger curse words, and it had a lot more blatant sex jokes, including a few episodes where the duo are portrayed as gay lovers. Needless to say, it didn't go down well...
To promote the movie, a PG-13 version of G.I. Joe called G.I. Joe: Resolute was launched [adult swim]. The first episode involves Cobra taking a massive boost in competence, leading to the Joe's battleship base attacked, Bazooka killed, and Moscow wiped off the face of the map. Then again, what do you expect when Warren Ellis is doing the writing?
There was also a version on The Hub called G.I. Joe: Renegades. While not as dark as Resolute, it certainly wasn't the kiddie-esque fare of the '80s cartoons.
However, the new series Scooby-Doo! Mystery Incorporated has become Darker and Edgier, again. And becomes more and more Darker and Edgier so as the series goes on.
Season 1 was no picnic for the gang, but Season 2 really takes a dark turn. The villains are generally more menacing, and the plot becoming more of a Cosmic Horror story. And then comes the Grand Finale, which has to be seen to be believed.
The recent movies have also returned to a darker tone and style. Basically, the franchise is perpetually on a Cerebus Rollercoaster.
The final episode of Tales from the Crypt (the only one animated) was a bloody and gory retelling of The Three Little Pigs, featuring the wolf messily eating the pigs (and presented as a rapist in one scene) and making two of the pigs a smoker and an alcoholic who sponge off their brother. Plus, The Bad Guy Wins.
The "Red Sky" seasons in the 1987 series is this compared to the light-hearted show before.
To expand on this, the last 3 seasons (starting with season 8) were dubbed the "Red Sky" seasons by fans, because the sky was always red, giving the show a more post-apocalyptic feel. There was a greater focus on action and less on Slapstick and Breaking the Fourth Wall. The turtles were also designed to look less Lighter and Softer. Here's a clip for those who aren't familiar with these seasons.
Strangely enough, Raphael becomes Darker and Edgier for a few seconds in the second intro of the 1987 series of Teenage Mutant Ninja Turtles. This happens during the long version of the intro when the Theme Song reaches about 18 seconds and happens right at the beginning in the short version. It's when the screen pans upward to Raphael's face. His shading is much darker than usual, not to mention having an angry glare in his eyes. Keep in mind that this version of Raphael is a levelheaded wise guy, unlike the usual portrayalofRaphael in most of the other TMNTcontinuities. With that said, this instance of an aggressive-looking '87 Raphael (pre-season 8) is actually quite fitting.
The Nickelodeon series is in-between, being more serious than the 80s one but lighter than the 2003 one.
Avatar: The Last Airbender features this after Season 1. While the first episodes did detail how a nation was destroyed and explains Zuko's scar, it's not until the second season when the plot really starts to hammer in the sheer destruction of war, touching on such cheery implications as genocide, concentration camps for water benders, and a general feeling of helplessness. In addition, the second season introduced the extremelycompetentPrincess Azula to follow up on the first season's Starter Villain. Even the personal stories get deeper and darker, with Zuko struggling with moral issues, Katara seeking vengeance for her mother's death with a technique called "bloodbending", and Azula going absolutely psychotic. Done well, because the descent into darkness is gradual and doesn't just put a gun in a character's hand. Rather, the focus is on fleshing out characters and exploring the implications of their situation.
The show is an excellent example of how a series can be dark, with mature themes, without having to resort to graphic content (something it shares with a number of other series, including Harry Potter).
The creators have even stated outright that Korra is darker and more mature in comparison to Airbender - which is extremely impressive for a Nickelodeon cartoon, given how mature the original series was already. So far, nothing has proven them wrong, with scenes that are highly reminiscent of public executions and rape, constant allusions to historic examples of oppression such as McCarthyism, the Red Scare, the Nazi suppression of Jews, etc. a politically driven storyline filled with social and political unrest and perhaps the most blatant depiction of a terrorist attack in the history of children's television.
A Murder-Suicide. Not implied or ambiguous, but fully shown in the season finale.
Season 2, just six episodes in, is far darker than even the first season. Rage Against the Mentor is in the first episode, Aang is revealed to have unintentionally neglected Kya and Bumi, a Civil War breaking out in the Water Tribes in an gigantic Cain and Abel struggle between Korra's Uncle and Father, Korra's Creepy Twins cousins Eska and Desna, Eska begins dating and enslaving Bolin and tried to force him to marry her and when he broke it off she pursued him with a Murder Face on, and we're revealed to a Crazy Awesome businessman named Varrick who bombs the Southern Water Tribe cultural center (with people most notably being in it) as well as his own ships so he can bankrupt Asami's struggling Future Industries and take it over! Oh and the cherry on top the heroine loses her memory after breaking up with the cop boyfriend and then being swallowed by a Kaiju sized Dark Spirit!
Season 3 started out dark with showing non-ambiguous suicidal thoughts, violent prison escapes, and a queen who forced irbenders into an army regardless of age, but once Korra meant the Red Lotus it got even darker than Books 1 and 2 combined. First off, a high ranking member of a city was a traitor and tried to kill Team Avatar WITH A BOMB. After the show was put online, the villains were revealed to be anarchists who believed the natural order is disorder and didn't wants rulers. The last 4 episodes were some of the darkest ever. To start off, Zaheer killed the Earth Queen in the most graphic death in the series by bending the air out of her lungs while giving her a chilling Hannibal Lecture. After doing that they broke down the wallsof Ba Sing Se and the city descended into chaos with looters robbing the palace and entire neighborhoods being burned down. The Red Lotus next tried to get their hands on Korra by threatening another Airbender genocide with P'Li being the cold sniper and nearly killing Kai. The episode also ended with Tenzin being on the receiving end of a No-Holds-Barred Beatdown. The finale had P'Li accidentally blowing herself up and her love Zaheer witnessing her death, Korra being poisoned with possibly mercury, Ghazan committing suicide to avoid reimprisonment, Ming-Hua getting electrocuted, and Zaheer going pretty much berserk. The finale ends with Korra broken physically and mentally from the poison and wheelchair bound and the story ends with a Single Tear from Korra who can barely talk, move, or smile. Basically, by the end of the book there were no more questions why this season was put online and not TV.
Sonic Sat AM to Adventures of Sonic the Hedgehog: The latter show was a light hearted comedic show without any of the characters being in any real danger while in SatAM, Dr. Robotnik has become a power hungry dictator who has taken over the city of Mobotropolis, captured the king and thrown him into another universe, and has turned most of the inhabitants into robots to do his bidding. He is also much more menacing and capable than his other interpretations, which are generally bumbling idiots. Also, Sonic, Tails and a band of surviving friends known as the Freedom Fighters try to stop him from completely taking over the world- he already owns most of it -and must avoid being captured and roboticized in the process.
Although it is MUCH lighter than the comic.
Parodied in The Stinger for the Ed, Edd n Eddy movie. Having been beaten up by the cul-de-sac kids over a misunderstanding (he attacked the Eds, not knowing that everyone had made up), Johnny, as his superhero persona Captain Melonhead, reimages himself as The Gourd and swears revenge on the neighborhood... only for Plank to tell him the movie was over.
The movie itself was a more Darker and Edgier version of the series, and not in the fun way: The Eds' scheme seriously wounded the other kids for once, which cause them to seek retribution, meaning ganging up on the Eds so they could beat them up senseless. The Eds themselves ends up in several hardships trying to escape them, which takes its tolls on both Edd and Eddy. They end up in a rather ugly fight because of Eddy's lack of seriousness and empathy unleashed all of Edd's repressed anger, and later it turned out that Eddy has his reasonsforhisbehavior. The climax itself was a horrific deconstruction of Amusing Injuries and what consequences they actually have.
Another episode that has a dark feel to it is the Cartoon Network Invaded special episode "The Eds Are Coming".
In addition to the direction of its writing, South Park's evolving animation style and loosening content restrictions imposed by the network played a major part in the show becoming darker (if not more serious) over its run, with more and more graphic content included on a regular basis. It's gotten to the point that most of the old episodes, which were once rated TV-MA, are now rated TV-14 since they appear downright tame compared to what's been allowed on the show (and other basic cable programming) in recent years.note Some of them are still Edited for Syndication in order to achieve said rating.
South Park: Bigger, Longer & Uncut was an early indication of some of the things the series would do in later years. To elucidate, there's a higher body count than the first three seasons combined (To be fair it does involve a war), Kyle's mom is a genuine, no-nonsense Big Bad and the global scale war and The End of the World as We Know It was treated dead seriously although some of the events that kick-start it e.g rampant cussing, the bombing of the Baldwins is pretty hilarious.
Some pretty dark and dramatic episodes, such as "The Return of Chef", "Stanley's Cup", "Imaginationland" trilogy (that is clearly more serious), "Coon & Friends" trilogy and "You're Getting Old" are clear examples that often the series goes from being Played for Laughs to Played for Drama. Try watching these episodes and then watch any episode from the season 1. There is a clear difference.
Spider-Man: The New Animated Series is perhaps the darkest telling of Spider-Man. The pilot alone portrays the origin of villain Electro as a tormented university student who smashes a sign after everyone laughs at a cruel prank played on him, is electrocuted, then murders the chief antagonist. Spider-Man tries to stop him from killing more people, Electro seeing everyone as the people who hurt him, but can only do so by killing him. Too bad, as the graphic nature was what killed the series.
The 1981 syndicated Spider-Man series was also darker and edgier compared to the Spider-Man and His Amazing Friends series shown on NBC's Saturday morning lineup at the same time.
The Rugrats Movie: Not too many fans (want to) remember the show containing murderous animals, child endangerment, and tension between the babies thick enough that it can be cut by a katana.
Rugrats: The 1991-1994 episodes, in comparision to the more child-friendly later seasons. Resulted in heavy 
This is taken up to eleven in the Snow White Segment of Rugrats: Tales from the Crib when Angelica (as the Evil Queen) not only threatens to slit Snow White's throat a few times (only to be corrected that it's aimed at a family audience), but also refers to Kimi as "Spazzy".
It's also a bad sign when the adults are being more competent than usual.
Teen Titans got darker with each season, starting out mainly as an action-comedy cartoon with only the Robin-centric episodes being serious, but after the first season it all went downhill from there, and you got episodes like Robin going temporarily insane, Terra "dying" and then later maybe possibly coming back to life?, and then there was the apocalypse with everyone turning to stone.
All of the arc episodes in Raven's season (a.k.a. season four) were Cerebus Syndrome incarnate. How bad is it? Well, Slade comes back to life, has pyrokinesis, and is after Raven in a seriously Pedobear way. And that's just the first arc episode.
J. Torres: [The show] started out skewed a lot younger... but along the way, I think the producers discovered it was reaching a wider audience. ... [the show] got into some darker story lines, and they introduced a lot more characters, so they expanded on it, and they let the show evolve with the audience.
Thomas the Tank Engine: Season Five. It had several scary and adventurous episodes. Nothing too gratuitous of course (it is a kids show after all).
The Boondocks TV series in comparison to the comic strip its based on. Though justified in that being on television obviously allows it to get away with a lot more than what a daily newspaper comic strip would.
There was also the student film "Bring Me The Head Of Charlie Brown" by future Simpsons writer Jim Reardon, which involves the Great Pumpkin hiring the kids as hitmen to kill Charlie Brown in gruesome ways, eventually he snaps and goes on a killing spree.
When Batman: The Animated Series started in 1992, it was this compared to every other kids show out there. In a good way though, with mature storylines and complex characters and themes. The movies were even darker.
While Phineas and Ferb is a funny and light-hearted in its own right, the show's first half-hour episode (and season one finale), "Phineas And Ferb Get Busted" is among the darkest things Disney has ever done. After Candace successfully busts her brothers, the duo get sent to a reform school that's a prison where their identities and creativity are stripped and they are subject to Clockwork Orange-esque torture and a not-so-subtle form of waterboarding, to the point of becoming imagination-deprived zombies. Candace eventually discovers what's going on and attempts a rescue, where she is barely able to save them. Bonus points for the fact that the reformatory's Drill Sergeant Nasty is perhaps one of the most evil villains to appear in a Disney cartoon, to the point where he even gets killed at the end. Thankfully, it's All Just a Dream (within a dream), but it's still a terrifying What If? episode.
The movie is also this. It involves the first time where Phineas is truly mad at someone (him being upset at Perry revealing himself to be a secret agent, as he feels like Perry never regarded him and Ferb as friends), we have a dictatorship where every character has Darker and Edgier counterparts, and the first time the main characters have been faced with someone trying to kill them.
To a lesser extent, the fourth season as a whole seems to be more liberal when it comes to using black comedy and Getting Crap Past the Radar, and the stories of some episodes may count too, in particular Phineas' controversial snapping in "Mission Marvel".
It's been noted that the series has been getting Darker and Edgier as it goes along, too. While the main villain from season one was forgiven, Season 2's Discord was put back in the Fate Worse than Deaththat he came from, and in the third season's premiere, the villain is outright killed. This coincides with and is somewhat justified by each of these villains in turn being less sympathetic than the last (angry and frustrated moon princess, jerkassish and unempathetic but still somewhat amusing spirit of chaos, egotistical and sadistic shape-shifting Queen, blackhearted unicorn king who enslaved his subjects seemingly just for the evulz...), though of course that's still this trope. Trend possibly averted with the main villain of the season 2 finale, though, even if she and her army haven't been seen since — merely being blasted over the horizon should by rights be only an inconvenience for cartoon villains with wings. As for one-parters, we have season 3's "Magic Duel", where Trixie, who in season 1 was a mostly harmless Miles GloriosusJerk Ass, comes back under the control of an Artifact of Doom, inflicts various types of Body Horror on the characters, forces Twilight Sparkle, the only character capable of saving them, out of town and turns Ponyville into a dictatorship where everypony is her slave.
An in-universe example in King of the Hill: Multiple episodes show Luanne running a Bible-themed puppet show called "The Manger Babies". In a later episode, John Redcorn runs a business of selling children's educational DVDs and has Luanne make some. When her popularity wanes, she tries to gain back her fanbase by making a Darker and Edgier show with "edgier" storylines and characters, including a Bratz doll Expy.
"Pigmalion", to elaborate Luanne gets a job at a millionaire's house and moves in with him, at first things are fine but after a while he starts to get very obsessive and creepy, he dyes her hair and won't let her wear anything but identical dresses, it turns out to be an insane plot about his vision of "the perfect family" which consists of her and a man dressed in a Swiss outfit and himself as their pet pig, this scares Luanne and he chases her into a pork processing plant where he ends up being killed by the processing machine.
In The Simpsons, This scene, once you get to the sweatshop part, in comparison to other Simpsons scenes in general, let alone Simpsons intros. It could easily be considered the darkest sofa gags in the entire series, and one of the darker scenes.
The first Treehouse of Horror was a series of moderately creepy stories connected by a non-frightening Framing Device which kept reminding viewers that the tales were fictional. Starting with the second special, however, the stories began to get more violent and scary while the Framing Device got less and less reassuring. Eventually it was dropped altogether, and the stories quickly became downright horrific.
"Homer's Enemy". Is considered by some fans as one of the darkest episodes of The Simpsons, although many also counts as an episode to which he added more Black Humor.
Any episode with a character who has no funny quirks and is played seriously. Examples include the french winemakers from "The Crepes Of Wrath" (who nearly killed Bart by giving him antfreeze-laced wine not to mention that their general treatment of him was pretty poor), the Babysitter Bandit from "Some Enchanted Evening" (who tied up the kids and tried to rob the house) and Bart's kindergarten teacher from "Lisa's Sax" (whose treatment of Bart made him what he is today).
Some episodes with Mr. Burns are darker and more dramatic than any other episodes (except the ones mentioned here). Examples include "Raging Abe Simpson and His Grumbling Grandson in The Curse of the Flying Hellfish" (where he crossed Moral Event Horizon by trying to drown Bart), "Who Shot Mr. Burns?" (where he blocked all the sunlight from Springfield, and he screwed over other characters in the same episode and his action were played seriously. It makes his shooting look justifiable.), "Mother Simpson" (where he was involved with biological warfare and he is responsible for making Homer's mother, Mona Simpson, to run from the law, even though she saved him). As you can see like Bart's unhappy kinder gardening, Mr Burn's actions also set future episodes in motion...
The earlier Sideshow Bob episodes were also quite dark and dramatic. This eventually went away after his gradual Villain Decay.
The darkest episode has to be The Sting, with its death of Fry moment, Leela's hallucinations, and her almost-suicide. As well, the episode is favored as a clearer view of Leela's unrevealed affection for Fry and Philip's not-as-dumb-as-seems devotion to her.
Recess, despite being a light-hearted show about group of kids and their adventures at school, had a few dark and serious episodes.
"Prickly Is Leaving". We were introduced to Dr. Slicer: the most evil villain in the series, who employed cruel and unusual tactics to control the school and, unlike Finster or Prickly, only cared about power without regard for the students' welfare. His behavior even disgusted Miss Finster, and TJ (who was never afraid to stand up to adults before or since) was completely scared of him. He was ousted in the end, but consider this: Third Street wasn't the first school he was principal of, and likely would not be the last.
"The Biggest Trouble Ever" is a Wham Episode for the series. It involves the gang accidentally breaking the statue of Thaddeus T. Third III and become the town's most hated people. Ms. Finster punishes them by making them work menial jobs. But the real reason why the episode is so dark is what happens later: Mayor Fitzhugh, the mayor of Third Street, decides to send the Recess Gang to six separate schools, even though they were remorseful and even Prickly and Ms. Finster objected. Throughout the episode, Fitzhugh looked very gleefully sadistic about the whole thing, and only relented when Third's own grandson, demanding that they be pardoned, threatened to expose Fitzhugh's own (deliberate) past misbehavior regarding the statue.
The Halloween special is really quite creepy, especially for a show aimed at kids. It's presented in an anthology format (similar to the Treehouse of Horror episodes of The Simpsons): One story features a recurring character becoming a werewolf and attacking various citizens, the second (in a homage to Stephen King's Christine), has the kids' bicycles coming to life during a storm, causing fear and chaos (this even ends with a sinister cliffhanger, as the bus the school escapes on is revealed to be similarly alive), and the final story features the gang being pursued by zombies, very creepy ones at that.
The Rise of Miss Power is this to the regular WordGirl series. While there are still jokes, we are introduced to the villainess Miss Power, who, unlike other villains, is taken seriously. She goes to Earth, and teaches WordGirl her powers (like ice breath), and also teaches her to mock the other villains. This goes so far as to WordGirl/Becky Botsford talking back to her parents, and she even mocks her own sidekick. When she discovers Miss Power's scheme, she gets a No-Holds-Barred Beatdown, and is declared to be weak by Miss Power, and she takes over the town. And, unlike other villains, she would've succeeded in killing someone, had WordGirl not intervened, and almost succeeded in taking over the world. This feeling towards the episode is mostly because of the anti-bullying message they put into the movie.
Miss Martian is now an Anti-Hero who regularly extracts information from her enemies' minds, even though it leaves them completely catatonic. Superboy (now her ex-boyfriend) is increasingly concerned, and the fact that she tried to make him forget he was upset was the last straw before the breakup.
Aqualad's arc isn't any lighter. When he first appears, it's set up to look like he switched sides during the Time Skip, and he nukes a base full of oblivious krolotean henchmen just to make it convincing. Then it turns out he's a Fake Defector and picked warning his friends about the bomb over saving the aliens, but Nightwing still notes that it was an "impossible choice". He is then mind-raped by M'gann.
Have fun watching Artemis's Team and family mourning her death and swearing vengeance on the killer!
And it gets worse with the revelation that Jason Todd existed in Young Justice and was introduced and killed off during the time skip. Not enough terror yet? Think about the emotional effects of that on Nightwing coupled with everything else that's been going on. Can you say "impending mental breakdown"?
The closer two episodes take the cake. "Summit" shows a character get stabbed with blood on the exit wound (granted, it was Ra's Al Ghul). And in the second season finale, Kid Flash disintegrated very painfully on-screen, being very definitely Killed Off for Real.
The Grand Finale of Kim Possible could probably qualify. Not only are all the main locations of the series destroyed, but the Take Over the World scheme is more destructive than any other, and on top of that, the hero comes closest to dying. Oh, and did we mention that it also contains the only real time when the villains of the episode are Killed Off for Real? Granted, they were more dangerous than the other villains that the series showed and they weren't humans, but still.
X-Men was a pleasant surprise when it first hit TV. It had the death of one of the main characters in the first episode, dealt with prejudice and interpersonal conflicts virtually unknown in a Saturday morning cartoon, portrayed bad futures, and took a more adult approach that treated viewers as mature.
Beavis and Butt-Head Do America. While the film still has comedic beats, the plot is much more serious than any episode of the series. A criminal confuses Beavis and Butthead for a couple of thugs he hired to kill his wife, Dallas. Dallas also hides an extremely dangerous biological weapon in Beavis' shorts. The CIA learns of this and starts to go after the duo. Given all of this, Beavis and Butthead have several brushes with death. In addition, a couple of scenes were somewhat sexual.
But still, in the final season the things really got worse, especially with the episode "The Mask", which is one of the most realistic depictions of domestic abuse in the villain Mad Dog. Also "Remembrance of Courage Past".
The first episode "House of Bloo" could count as well. There are much more serious and Tear Jerker moments than in next episodes, which clearly became Lighter and Softer.
In The Fairly OddParents, it is highly questionable that over time, the show has been become darker and edgier, perhaps on the verge of becoming this in season 2 or 3.
"Action Packed" is an example of this. Even the physics of the animation is darker and edgier when Timmy wished to be in an action movie.
The Movie titled Abra Catastrophe. Crocker is much more evil than in other episodes, even crossing the Moral Event Horizon when kidnaps and tortures Wanda for use as a power source. In fact, the consequences are quite threatening and Timmy has no choice that faces Crocker in a fight during the climax.
Also, any episode featuring a villain who is really evil away: "No Substitute For Crazy" with the appearance of Miss Doombringer: a crazy woman who is definitely worse than Mr.Crocker, and The Destructinator from the episode "Wishology".
In the episode Hassle In The Castle we're introduced to Maryanne who, despite being a one shot character, is probably one of the most evil characters ever to appear in a children's cartoon. She killed Franz Ferdinand and his wife For the Evulz and caused World War One.
In Daria, several episodes focused on Tom and his relationship with Jane and Daria are clearly darker.
The final episode entitled "Boxing Daria". It is probably the most serious and dark episode of the entire series and there is a significant Tear Jerker. And why? Because we found a Daria's tormented memory from her childhood, and has much to do with her personality. Unlike other episodes, contrasts comedic moments and the whole episode generally focuses on this topic.
The creator said about this episode, saying:
"Daria's journey was wrapped up in... [this] episode. Daria realizes that her isolation isn't just about being different - she likes being isolated. It may be painful for her, but she's better off trying to interact with the others. She's pretty realistic. She's smart and articulate yet unsure of how the world will accept her."
The Looney Tunes series went in this direction during the mid 1940's. The Disney-esque musical cartoons were all but abandoned, the jokes became meaner and more cynical, etc. "Fresh Airedale", "Each Dawn I Crow", "Long-Haired Hare", "Knights Must Fall", "Chow Hound" and "Hare Raising Hare" are among the darkest cartoons Warner Brothers ever produced. Around 1952, this toned down slightly, and there were more fluctuations between Darker and Edgier and Lighter and Softer (although 1964's "Dumb Patrol" was among the darkest Bugs Bunny cartoons ever made).
This goes back even further in some cases. For example, the Porky Pig cartoon "Pied Piper Porky" is surprisingly dark for a pre-1943 Porky Pig cartoon.
American Dad! has the episode "Hot Water". In it, Stan buys a living hot tub who alienated Stan from his family, then kills Lewis, Marguerite, Francine and Stan in that order. Something quite disturbing if the series has not been renewed after this episode, this would have been the end of the series. And while the episode was eased with some humor, The Bad Guy Wins this time and the living hot tub is actually a Karma Houdini.
Several episodes focused on Roger are clearly darker and edgier, deserves special mention "Love, American Dad Style", where Roger finally could say that crosses the moral event horizon with the extreme obsession for Hayley, at point who ultimately he shoots and tries to rip her skin. Most disturbing (but probably played for laughs) is that the episode ends with Roger getting away with it, ripping the skin to Jeff.
The episode "Son Of Stan" also deserves a mention, especially in the climax of the episode, where Stevearino (Steve's evil clon) reveals his True Colors: he has dedicated himself to kill cats For the Evulz, later he tries to kill his own brother and his father. Unlike Roger, he's played seriously.
The Christmas episodes. Most notably the two dealing with the Anti-Christ.
Barbie In A Mermaid Tale 2 is more serious than the first movie; despite Eris being deposed, the scenes of the characters' worst nightmares are pretty intense, and it has Merliah in the position of possibly losing her legs forever. There's also two scenes where Kylie almost drowns.
The episode Dreamscapers (and Gideon Rises, for that matter) of Gravity Falls is a WHOLE lot darker than the rest of the season. It had a MIND DEMON. Things took an EVEN DARKER turn when he got mad. EAT NIGHTMARES!
The short series Dipper's Guide to the Unexplained was mostly a short, lighthearted comedic bit of animation. However, the last episode The Hide Behind featured a real lumberjack legend (which is disturbingly similar to Slenderman), and even ended with him being real and stalking Dipper on the way home.
Dungeons & Dragons got noticeably Darker and Edgier in its second season (even the opening credits!). Sometimes it worked, by averting Angst? What Angst? and letting the kids actually show the emotional pain they would logically be feeling due to their circumstances. Other times, it drifted into Narm and seemed like a lot of cheap angst for its own sake. The third season pulled back to a tone midway between the first two.
The Snow Queen (2012) is darker than the fairy tale that inspired it; The Snow Queen rules the world as a dictator and plans to cause eternal winter everywhere.
DuckTales was mostly a light-hearted kids show, but it had a few dark episodes. The nephews were once turned into gold statues, and there also were several episodes, where a character nearly dies.
The alien robots in the episode "Money to burn" not only stole Scrooge's money bin, so they could melt down the coins to make new robots. But they also were really close to melting Scrooge and Launchpad into grease. Not to mention the Fridge Horror that these robots had probably killed off the alien race, who had once created them in the first place...
The mites in "The attack of the metal mites" were played very seriously, despite the fact that they were tiny insects. After all, they were designed to eat metal! So they caused plenty of damage all over the city, and they even devoured Fenton's otherwise indestructable Gizmoduck suit.