History YMMV / AdventureTIme

* CompleteMonster: The [[CrapsaccharineWorld seemingly sweet]] land of Ooo has many villains, but while many are either very [[TragicVillain tragic]] or [[PlayedForLaughs not serious]], the same cannot be said of the following:

** Generally people assume that facts about the normal world carry over to its gender bent counterpart--for example, that [[GodSaveUsFromTheQueen the Ice Queen]] knew [[TallDarkAndHandsome Marshal Lee]] during the Mushroom War. However, many fans depict the Ice Queen not as a female version of Simon Petrikov, but as his fiancée Betty, suggesting that [[ForWantOfANail in this world]] his "gag" was putting [[ArtifactOfDoom the crown]] on her instead of himself.

** [[Characters/AdventureTimeTheLich The Lich]] is an evil, ancient sorcerer, the "last scholar of GOLB", and the series's defining KnightOfCerebus who returns time and time again from seeming destruction focused solely on one thing: [[OmnicidalManiac the destruction of all life]].
*** [[EvilSorcerer The original Lich]] escapes his amber prison and attempts to use his well of power to restore his power and bring about the end of Ooo, only to be foiled by [[Characters/AdventureTimeFinn Finn]]. The Lich then possesses [[Characters/AdventureTimePrincessBubblegum Princess Bubblegum]] to [[DemonicPossession use her body]] for his purposes. The Lich later murders Billy in retribution for his past defeat, wearing his skin to trick Finn into giving him the Enchiridion so he can enter the Time Room and wish for the extinction of all life across the multiverse. The Lich spitefully murders [[BenevolentGenie Prismo]] and his physical body and tries to use an army of cosmic breakouts to destroy a billion worlds across the universe, turned into a harmless baby named Sweet P afterwards.

*** Comic Book: [[Characters/AdventureTimeTheLich The Lich]], as vile as in the cartoon, continues his crusade to [[OmnicidalManiac destroy all life]] after his defeat in [[Characters/AdventureTimePrincessBubblegum Princess Bubblegum]]'s body, taking physical form again to use a BagOfHolding to suck up thousands across Ooo, with the ultimate intent to suck up the entire planet and throw it all into the sun. Even destroyed, the remnants of the Lich's power continue to horrify and torment [[Characters/AdventureTimeFinn Finn]], with an echo of the Lich's power creating a dungeon to MindRape the heroes--taunting the [[Characters/AdventureTimeIceKing Ice King]]/Simon Petrikov with an image of his old love Betty and [[ForcedToWatch forcing him to watch]] as she fell apart--and twisted a sapient tree into a horrible monster, both in preparation to eventually recuperate and destroy life again.
** "[[Recap/AdventureTimeS7E37Preboot Preboot]]" & season 8's "Islands" miniseries: [[MadScientist Dr. Gross]] was formerly a scientist and doctor on the series of islands founded by Minerva Campbell as a refuge for the remnants of humanity, training children to become "Seekers", with no hesitation in brainwashing them and having them brutalize their own friends to prevent any escape from the islands. Dr. Gross eventually turned to twisted experiments on sapient beings, with her recklessness accidentally unleashing a virus that killed off two-thirds of all humanity on the islands--to her complete apathy. Escaping the islands, Gross [[EvilutionaryBiologist continued her experiments]], scheming to return to the islands and forcibly augment all humanity into cybernetic abominations like herself, even trying to cut apart [[Characters/AdventureTimeFinn Finn]] and his friends to use as raw material. An unfeeling scientist with [[LackOfEmpathy zero empathy]], Dr. Gross proves that, sometimes, HumansAreTheRealMonsters.

** Tree Trunks, while never exactly a fan favorite, was originally fairly well-liked due to her IntergenerationalFriendship with Finn and Jake, her [[NiceGirl kindhearted personality]], and being a CoolOldLady. While her DirtyOldWoman tendencies initially grossed out a few fans, especially since some of them were [[{{Ephebophile}} aimed at the 13 year-old Finn]], most were willing to write it off as harmless, helped by the fact that she never showed interest in Finn after her first two appearances, making it look like a case of EarlyInstallmentWeirdness. However, thanks to the [=#MeToo=] movement exposing how bad the DoubleStandard of [[PaedoHunt adult women grooming male children]] really is, an increasing amount of fans have come to regard Tree Trunks' crush on Finn as ''incredibly'' [[{{Squick}} creepy]]. Although she still has some fans who [[FanonDiscontinuity prefer to ignore her first two appearances]], several are unable to look past her early characterization to see her as a sweet old lady at all. As a result, she's become quite a [[BaseBreakingCharacter divisive character]], to say the least.

** Tree Trunks, while never exactly a fan favorite, was originally fairly well-liked due to her IntergenerationalFriendship with Finn and Jake, her [[NiceGirl kindhearted personality]], and being a CoolOldLady. While her DirtyOldWoman tendencies initially grossed out a few fans, especially since some of them were [[{{Ephebophile}} aimed at the 13 year-old Finn]], most were willing to write it off as harmless, helped by the fact that she never showed interest in Finn after her first two appearances, making it look like a case of EarlyInstallmentWeirdness. However, thanks to the [=#MeToo=] movement exposing how bad the DoubleStandard of [[PaedoHunt adult women grooming male children]] really is, an increasing amount of fans have come to regard Tree Trunks' crush on Finn as ''incredibly'' [[{{Squick}} creepy]], with many finding it hard to see her as a sweet old lady at all because of this. Although she still has some fans who [[FanonDiscontinuity prefer to ignore her first two appearances]], several are unable to look past her early characterization.

** Jake's son, [[CorruptCorporateExecutive Kim Kil Whan]], splits the fandom a lot. Either he's a JerkWithAHeartOfGold who only wants what's best for his family and teach them responsibility, or he's a completely unlikable and amoral {{jerkass}} whose [[WellIntentionedExtremist Well-Intentioned Extremism]] in his debut feature and the generally cold treatment of certain situations makes him a [[TheScrappy Scrappy]].

** Jake's son, [[CorruptCorporateExecutive Kim Kil Whan]], splits the fandom a lot. Either he's a JerkWithAHeartOfGold who only wants what's best for his family and teach them responsibility, or he's a completely unlikable and amoral {{jerkass}} whose [[WellIntentionedExtremist Well-Intentioned Extremism]] in his debut feature and the generally cold treatment of certain situations makes him a HateSink.

** Jake's son, [[CorruptCorporateExecutive Kim Kil Whan]] splits the fandom a lot. Either he's a JerkWithAHeartOfGold who only wants what's best for his family and teach them responsibility, or he's a completely unlikable and amoral {{jerkass}} whose WellIntentionedExtremist actions in his debut feature and the generally cold treatment of certain situations make him a HateSink.

** "[[Recap/AdventureTimeS1E13CityOfThieves City Of Thieves]]": [[BitchInSheepsClothing Penny]] is a thief and resident of the titular city. Taking advantage of Finn's heroic nature, Penny plays the part of a helpless little girl, tricking him into stealing the King of Thieves' treasure chest for her under the claim that it contained her stolen flower basket. After escaping with the treasure, Finn and Jake soon find Penny and scrub her down in an attempt to purify her. Penny then seemingly goes through a HeelFaceTurn, only to run off with Finn's clothes [[KarmaHoudini and continue her thieving lifestyle]].

** Several episodes like Bad Little Boy and Mystery Dungeon show that Ice King wishes for his fan fiction characters (Fionna and Cake to become a reality). Come 2023, [[WesternAnimation/AdventureTimeFionnaAndCake he would get his wish]].

* HeartwarmingInHindsight: "The More You Moe, the Moe You Know" was the last episode to feature [=BMO=]'s creator Moe and ended with [=BMO=] reflecting on his right of passage after defeating [=AMO=] to avenge Moe. In light of the passing of Moe's voice actor Chuck [=McCann=], the episode comes off as a touching send-off to Chuck [=McCann=].

** For many, Bubblegum comes across as this regarding her more morally dubious actions, at least in regards to her citizens. While she's meant to be seen as a morally bankrupt individual and ControlFreak, her citizens are shown time and time again to be ''too stupid'' to function without her, easily falling for con artists like the King of Ooo, getting themselves into trouble if she isn't constantly monitoring them, and being blind to danger like her test for the Banana Guards in "Root Beer Guy" or "Nemesis", which only results in them growing unruly and organizing secret protest groups. And while [[spoiler:she ''did'' make them that stupid to begin with, its shown with Gumbald and Chicle that they're naturally {{jerkass}}es otherwise, something carried over by the smarter Candy People eventually becoming the same like with Starchy]], making it harder for many to judge her ''specifically'' for how she treats her citizens when said citizens are more often than not ''a pain in the ass''.

* UnintentionallySympathetic: Lemongrab was this in "Too Young," because he appears to be severely mentally handicapped and had a job he was incapable of doing right (ruling a kingdom). Finn and Princess Bubblegum are disproportionately hard on him, up to the point of actually beating him up and making him cry. Averted in later episodes, where A) Princess Bubblegum helps Lemongrab, and B) Lemongrab is genuinely being a horrible person and deserves what's coming to him.

* SeinfeldIsUnfunny: This was the show that popularized the trend of animated children's series with ThinLineAnimation, CerebusSyndrome, and an ongoing story arc. With later shows like ''WesternAnimation/GravityFalls'', ''WesternAnimation/StevenUniverse'', and ''WesternAnimation/TheOwlHouse'' following in its footsteps, ''Adventure Time'' might not feel as special to people who watched them first.

** Finn's reaction to his dad's leg being burned off by a laser is to repeately yell "Uh-oh!", even after his dad assures him that he'll be all right.