History CerebusSyndrome / WesternAnimation

** The show itself has been through this not once or twice, but six times. The first season was more of a lighthearted, slice of life comedy show in the vein of WesternAnimation/TheSimpsons and WesternAnimation/BabyBlues which featured storylines focusing on mainly the family as a whole. The second season continued this formula but shifted it a little in favor of focus on other characters and started to find its own voice away from WesternAnimation/TheSimpsons. The third season is when the show began developing the characters but focused more on gags and jokes than the previous seasons and became edgier in tone. Seasons 4 and 5 had most of the character's personalities altered and became a show exclusively for telling jokes and gags but retaining some of the heart that the previous seasons had. This was altered again in Seasons 6 and 7 (mainly because the crew members that worked on Seasons 4 and 5 went to work on ''WesternAnimation/PhineasAndFerb'' and the majority of the "charm" those seasons had went straight to that show), where the show became a venue for jokes with very little heart in between and became a little more serious as some episodes had Brian voice Creator/SethMacFarlane's political views. They shifted this again in Seasons 8 onward in exchange for nothing but mean-spirited humor and taking a DarkerAndEdgier tone to the point of where an episode featuring heart now is very rare.

* This is the formula for most ''WesternAnimation/TeenTitans'' seasons; they start out light-hearted and comedy-driven, then become really dark near the end. The most extreme example compared to the rest of the show (the arc itself starts dark and stays there) is season 4, when Raven is used as a portal for her demonic father Trigon and he takes over the world in a hellish apocalypse where all humans except the four remaining Titans turned to stone. (This lasts for three episodes.) It's worth noting that the silliest stories usually came after a particularly dark or scary episode.

* ''WesternAnimation/RickAndMorty'': The ''even'' season finales are this trope while the odd season finales end on positive conclusions. And then the beginning of each season undoes any character development as Rick uses extreme hijinks to undo any permanent changes.

* While [[HalfArcSeason the structure of the series]] downplays this somewhat, ''WesternAnimation/{{Amphibia}}'' nevertheless undergoes this in its third season. Following the events of the season two finale, the show's final season sees it shift from what had been assumed to be the {{series goal}} of getting Anne and her friends back to Earth. Instead, with Anne having returned to Earth and Sasha still in Amphibia, they must stop the machinations of a tyrant king who wishes to conquer the multiverse with the help of his master, [[EldritchAbomination The Core]] who is controlling Marcy's body and using her as a puppet.

* ''WesternAnimation/TheOwlHouse'' may have accomplished beating the aforementioned ''Gravity Falls'' on this, being one of, if not '''the''' darkest Disney show ever released. The first season of the show, though loaded with horror elements, is mainly episodic, and any traumatic experiences that the kids go through are PlayedForLaughs, and get brushed off by them by the next episode. The show, however, gets steadily darker, even by the time of season 1B, with the reveals of [[WeUsedToBeFriends broken friendships,]] AbusiveParents, and sibling treachery. In season 2A, the main protagonist's GuiltComplex plays a critical role in the first episode of the season and the mid-season finale, the deuteragonist and her sister and the main protagonist's LoveInterest and [[spoiler:later girlfriend]] have visible parental issues brought to the forefront. But things really take a darker turn in season 2B once it is revealed that [[spoiler:the main protagonist's father died before the series and especially so once it's revealed that the Big Bad's plan entails full-on '''[[FinalSolution genocide]]''', which is shown in the season finale, and that he's been cloning his supposed nephew repeatedly and has killed each one so far, and is implied to have murdered his brother for falling in love with a member of the local MageSpecies]] By the time of season 3, [[spoiler:the events of the previous season have left the protagonist in a depressive state implied to be bordering on suicidal ideation, and the BigBad ends up [[DemonicPossession possessing and nearly killing his aforementioned nephew again in one of the show's most horrifying scenes.]]]] [[WhatDoYouMeanItsForKids And this is supposed to be a Disney show!]]

* Interestingly subverted by ''WesternAnimation/TheVentureBrothers''. The plot does get deeper and darker, but the comedy just gets blacker. Even utterly serious scenes don't stop with the jokes, the subject matter just shifts.
** Really, there is much more hope for the characters now than at the beginning.

* Relatively minor example, but although Season 8 of ''WesternAnimation/{{Archer}}'' (subtitled ''[[AdventuresInComaland Dreamland]]'') is still more comedic than dramatic, it does have a mostly serious FilmNoir mystery at its core, and contains lengthy scenes without a single joke. In Season 11, despite Archer waking up from his coma, the show still doesn't completely return to pure comedy, instead exploring the SurprisinglyRealisticOutcome that happens when the main character has been in a coma for a few years, as well as analyzing and occasionally deconstructing his social maladjustment and dysfunctional relationship with his coworkers (and their own dysfunctional relationships with each other).

** The sequel movie and epilogue season ''Steven Universe Future'', features a now-teenage Steven, having ended the war between his adoptive family of Crystal Gems on Earth and the fascistic Diamond Authority on the Gem Homeworld and brought peace to the universe, struggling to find purpose and meaning in his life, watching his formerly close-knit family and peer group grow apart and move on with their lives, and the creeping realisation that his adventures as a KidHero have left lasting, unresolved emotional trauma and PTSD, which manifests as Steven losing control of his powers.

* ''WesternAnimation/AvatarTheLastAirbender'' gets more angsty in each season. This is more the characters coming to realize things are bad rather than the plot getting heavier. After all, by the third episode, the show had established the lead character as the lone survivor of a genocide. The series also started adding far more dangerous enemies, going from the [[AntiVillain Prince]] [[IneffectualSympatheticVillain Zuko]] and [[SmugSnake Admiral Zhao]] in the first season to Zuko's sister [[MagnificentBastard Princess]] [[HeroKiller Azula]] in the second season and father [[EvilOverlord Firelord]] [[AbusiveParents Ozai]] in the final season. In spite of all this, the series never lost its sense of humour, preventing it from falling too deep.

* ''WesternAnimation/TangledTheSeries'' starts out as one might expect a ''Franchise/DisneyPrincess'' spinoff TV show to begin, with Rapunzel & co. going on miscellaneous adventures in Corona and learning life lessons. Then comes the season one mid-season special, "Queen For A Day." After [[spoiler: Frederic and Arianna are nearly killed in a blizzard]] and [[spoiler: Varian loses his father, thus swearing vengeance upon Rapunzel and every other person who stands in his way]]...it becomes pretty obvious the show is no ordinary sweet and light princess story, and from that point on the main overarching plot involving the Black Rocks and the mystery behind them becomes the forefront of the series.

* ''WesternAnimation/StarWarsTheCloneWars'' was hit by this, though due to the show's initial use of AnachronicOrder, things were lot bumpier. Generally, the first season is lighthearted fun, with a tinge of drama. Then comes the season one finale, ending with a terrorist attack. This sets the tone for most of Season 2, which featured massive scale combat chock full of FamilyUnfriendlyViolence, suicide, zombies, and child soldiers. Despite this, it still managed to stay kid-friendly and have its fair share of lighter moments. Then the middle of Season 3 gave us the Nightsisters and Brothers arc and the Mortis arc back to back, and the Cerebus Syndrome fully settled in. While Season 4 had a few lighthearted episodes where C-3PO and R2 had fun adventures, the rest of the season was filled with violent deaths (one character breaks a mook's neck, for Pete's sake), scenes of war, and racism towards clones, all capped off with a restored [[KnightOfCerebus Maul]] beginning a galaxy wide murder spree ([[WouldHurtAChild no children spared]]) in pursuit of vengeance. And Season 5 didn't let up on this, all the way to the conclusion which featured [[spoiler: Ashoka framed for a terrorist act, slated for execution, and then leaving the Jedi Order upon her name being cleared. The next two seasons only get darker and darker by continuing to show more violence, more conflicting ideology, and more story arcs (including the final arc of the series) [[DownerEnding ending on a tragic note]].]]

* ''WesternAnimation/StarVsTheForcesOfEvil'' was originally a lighthearted, if occasionally dark, comedy about a "magical princess from another dimension" who was exiled to Earth in order to learn how to control her powers. Then came the introduction of [[KnightOfCerebus Toffee]] halfway through the first season, who pushed aside the show's IneffectualSympatheticVillain to become a major threat to magic itself by the end of the second season. The final two seasons would then pull a realistic twist on the show's {{fantastic racism}}, examine the politics of Star's home dimension, and explore the various romantic relationships between the characters.