[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/adventure_time_gainax_ending.png]]
[[caption-width-right:350:"If sweetness can win, ''and it can'', then I'll still be here tomorrow to high-five you yesterday, my friends. Peace!"]]
''WesternAnimation/AdventureTime'' has so many [[GainaxEnding weird episode endings]] that it gained its own page.

Of course, since these are endings, ''unmarked spoilers ahoy!''
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* The "Tree Trunks" episode ends with the eponymous guest character taking a bite from the Crystal Gem Apple they've been pursuing all episode. She explodes. [[EsotericHappyEnding Then we see her running, laughing, through crystal.]] Fortunately, that one got a MindScrewdriver in "Crystals Have Power". Though, there's always the NoEnding original airing variant found on the ''My Two Favorite People'' DVD, where the episode ends as soon as Tree Trunks explodes; no walking through crystal which is actually how the original version of the ending was supposed to be.
* Mixed with NoEnding in "Evicted!". After a whole episode of dealing with [[CuteMonsterGirl Marceline]] taking over Finn and Jake's house, she gives it back... and they return to find a giant worm that blasts them with a ray of some sort and asks them to hug it. It got a MindScrewdriver of sorts in "King Worm"... three seasons later! (And it ''also'' had an ambiguous ending, since it mirrored the final scene from "Evicted!".)
* At the end of "Power Animal", Jake suddenly says "[[LampshadeHanging Let's]] [[LetsMeetTheMeat go eat Cinnamon Bun!]]"
* There was another one in "[[https://www.youtube.com/watch?v=RVXAqJQf6K4#t=10m20s The Chamber of Frozen Blades]]" when Gunter, one of the Ice King's penguins that he took to the hospital, lays an egg that hatches... into a floating, pink cat. Then the Ice King says, "[[NoodleIncident Gunter, why didn't you tell me?]]" ''[[NoodleIncident (Gunter says "Wa-wa-wa" as if to say "I don't know")]]'' "[[NoodleIncident Oh-ho-ho, Gunter-]]" as he is interrupted by Finn and Jake both kicking him. (While the cat would appear in later episodes, and it's revealed that Gunther is [[spoiler:an EldritchAbomination that existed for eons and was banished to Earth and [[SealedEvilInATeddyBear trapped in the body of a penguin]]]], but still no proper explanation for the cat).
* The end of "Her Parents" when Finn and Jake taste [[https://www.youtube.com/watch?v=a3NRzcn2PuI "Soy People,"]] which is said to taste exactly like humans... of which Finn is the last. Not at all helped by Jake actually saying, "Finn, you taste delicious!". [[http://youtu.be/a3NRzcn2PuI?t=37s Then Finn tastes it and grins as the background music slowly tenses and gets louder, to the point where it gets]] [[LoudnessWar distorted enough to blow out a speaker]].
* In "The Other Tarts," the psychotic Tart Toter bursts into the castle, brandishing a chicken and a squirrel in place of tarts, foaming at the mouth. He says: "This cosmic dance bursting with decadence and withheld permissions twists all our arms collectively, but... If sweetness can win, (and it can!), then I'll still be here tomorrow to high-five you, yesterday, my friends. Peace." As he says this, the camera zooms in on his deranged, foaming face, and fades to the Tart Toter's delusion of drifting through space, surrounded by sweets, and LSP is in the space background, taking a donut. All of a sudden, it cuts back to the castle, where Finn cringes and says "Geesh...", and the episode ends.
* "Guardians of Sunshine" randomly ends with a "Game Over" screen. Note that Finn and Jake had already escaped from the video game by that point.
* "Vault of Bones" ends with Flame Princess finally managing to open the treasure chest that she and Finn have been trying to get into for most of the episode. It contains a green living creature that looks like a pair of buttocks, which winks at her. End credits.
* "Princess Potluck" ends with Jake getting randomly shot at the back of his head with an arrow by [[CallBack the squirrel from "The Duke"]], who has suffered, pardon the understatement, '''''[[ChewingTheScenery massive]]''''' SanitySlippage.
-->'''Squirrel:''' ''YOU SON OF A BLEEBLOB!'' '''''JAAAAAAAAAAAAAAAAAAAAAKE!!!'''''\\
'''Jake:''' ''(not recognizing the squirrel)'' Heey... yooooou.
* "Shh!" abruptly ends with a DancePartyEnding... and then Party God (yet another CallBack, this time to "Power Animal") comes in and crashes it.
* "The New Frontier" ends with Finn pretending to be a ghost while chasing Jake around the cave, and right afterwards comes a [[EsotericHappyEnding short sequence containing Banana Man doing a dance against a multicolored background]]. Note that before the sequence began, Banana Man was shown passed out in the pool.
* "Hug Wolf" ends with Finn managing to defeat the Alpha Hug Wolf who turns back into a female humanoid. Jake asks her for a hug, to which she suddenly turns into the tree monster from earlier. Cue Jake screaming, cut to black.
* "Box Prince". Finn gazes at the remains of the "kingdom" with the cats playing around and wonders if it even was a kingdom. The cats then dog-pile on Finn and purr. The end.
* "Breezy" ends with Finn and Breezy singing together about their love, which somehow causes the flower where Finn's arm used to be turn into a tree and explode, inexplicably regenerating his arm in the process. [[UnresolvedSexualTension Then the episode suddenly ends without Finn and Breezy's relationship being resolved.]]
** Despite Finn's hand being restored and his vision never actually explained, his relationship with Breezy is resolved because she was in love with the flower on his hand, and not him. After Finn and the flower are separated, she stops having any interest in him.
** Another weird thing about this episode's ending is that immediately before this, it is strongly implied that Finn had sex with Lumpy Space Princess. They may have just been kissing, but it's ambiguous.
* "Mama Said" ends with three Banana Guards knocking the King of Ooo unconscious by pushing him down a flight of stairs while he sits on a pizza that he believes may be able to fly. The guards then awkwardly break into the song "Mama Said" by The Shirelles, for some reason.
* "Blank-Eyed Girl" ends with the six Blank-Eyed Girls revealing that their huge blank eyes are just giant contact lenses and they had normal eyes underneath, then they reveal that their hair isn't real, and then they unscrew their heads and shed their bodies, revealing them to be [[StarfishAliens featureless, star-shaped beings]] who leave Finn and Jake's house through the window and break up into dandelion seeds. Finn and Jake are completely baffled, while BMO finds it beautiful.