In "Trouble in Lumpy Space", there's a conversation where Finn thinks Jake (in the throes of the Lumps) is about to request this of Finn, should he go completely Lumpy. It's never actually stated, and it turns out that Jake just wanted Finn to still be friends with a Lumpy Jake. "What did you think I was saying?"
Parodied in "Holly Jolly Secrets", where Beemo can't press the snooze button for his alarm function himself. It's against his programming.
Ice Cream Koan: The Royal Tart Toter's speech at the Royal Meeting. Justified, as he is very senile.
Royal Tart Toter: "This cosmic dance of bursting 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 friend. Peace."
If I Had a Nickel: After he frees Tree Trunks from the power of a crystal apple, Jake tells Tree Trunks if he had a penny for every time someone has been driven mad with magic power... he'd be Abraham Lincoln.
I'll Tell You When I've Had Enough!: Happens to Clarence after Ghost Princess dies. He does nothing but eat soft cheese... until he explodes.
I'm a Humanitarian: Lady Rainicorn's parents try to eat Finn, and are later seen enjoying a soy-based human substitute. Which they share with Finn and Jake, who both find it delicious.
Implausible Deniability: Happens with Jake and the Witch in "The Witch's Garden", but, to be fair, Jake didn't know that he did the crime for a moment; his subconscious was hungry, apparently.
Jake: I never ate your donuts. Witch: Well, you're eating one right now! Jake:(mouth stuffed and holding a donut) No, I'm not...
Impossible Thief: In "City of Thieves", Penny steals the clothes off of Finn's back without him even noticing.
Impossibly Delicious Food: The tarts. So much that they require a special transport chamber to carry them through, or "tart burglars" will try to steal them.
In-Joke: Several to character designer Natasha Allegri's cat Pancake, both visual and spoken.
Incredibly Lame Pun: The ending of "Loyalty to the King", after Finn reveals the Nice King to be the Ice King by gluing his shaved beard back on.
Finn: Now that's what I call a close shave. Jake:(Shakes his head while chuckling through Face Palm)
From "Beautopia":
Jake: Hey, what kinda coffee do you want? Finn: Hazelnut! Hazelnut! ...What if your name was Zelnut? And then I would be like, "Hey, Zelnut!" Jake: That's terrible... Finn: Hey, Zelnut! Jake:Noooooo! STOP!
Ink Suit Actor: Ricardio may well be the creepiest example ever. Basically, take George Takei's face, and paste it, in frightening detail, on an animated heart.
Innocent Innuendo: In "Fionna and Cake" shortly after Cake sends Fionna off alone with Prince Gumball to his room, she begins hearing strange noises that sound suspiciously like rape, but is actually Fionna fighting Ice Queen.
(from far away) Urgh, URGH! GET IT OFF ME! Cake:FIONNA?!
The entire episode of "The Chamber of Frozen Blades".
Invisible Wall: Beemo's video game Guardians of Sunshine has this feature; it represents the edge of the screen.
Invisible Monsters: Forget that; Finn and Jake go through an entire invisible obstacle course in "Rainy Day Daydream" which only Jake could see because it was in his imagination. "A bowl of baby elephants, chainsaws, and doo-doo's flying towards us! JUMP, DUDE!" Soon they come to a completely invisible monster, who can't be seen by either Finn or Jake.
Irony: The fact that a post-apocalyptic world could be so bright, colorful, and happy (most of the time). Pen has pointed this out numerous times.
Irritation Is the Sincerest Form of Flattery: Played with in "In Your Footsteps", in which a bear starts immitating Finn. Finn doesn't have a problem with it until he believes the bear is trying to outright impersonate him. It turns out neither one was the bear's real goal.
It Got Worse: "From Bad to Worse". The Candy Kingdom gets stricken with a zombie epidemic. Okay, nothing that hasn't happened before... except this time, Princess Bubblegum (AKA the only one who knows how to make the decorpsinator serum) gets zombified as well.
And then Finn's, Jake's, Lady Rainicorn's, and Lumpy Space Princess's attempts to make the serum cause the zombies to grow wings, become incredibly strong, and get awesome lips.
It Was Here, I Swear: Repeatedly subverted in "In Your Footsteps". Each time the bear does something strange, someone acts like this trope is in effect, only for it to turn out everyone already believes them.
It's All My Fault: Finn's exact words when his plan to carry the tarts through the Desert of Doom fails.
Donny, at the beginning of his episode of the same name.
Xergiok.
Marceline's ghost friends, Wendy, Booboo, and Georgy. They didn't care whether Finn and Jake died and actually intentionally attempted to suck out their guts as a joke.
Sir Slicer.
Marceline's ex-boyfriend Ash, big time. He sold Marceline's prized possession, a teddy bear she'd had since she was a little girl, to a witch for himself and wonders why she breaks up with him! Plus, he tricked Finn and Jake into making Marceline forget that he's a jerkass.
While to a lesser extent, Jake and the Ice King work this trope. Jake embodied this trope in "Party Animal" and City of Thieves" when he, despite good intentions, did a lot of harm. The Ice King is ultimately a lonely man looking for love who is Not Evil, Just Misunderstood and a Tragic Villain. His actions are extreme but his goals don't involve anything completely evil.
Just Eat Gilligan: Averted in "The Limit". Jake actually suggests stretching over the maze to skip the obstacles, but Finn points out the sign that says "NO CHEATING OR YOU DIE".
Karma Houdini: LSP could be considered one in "Trouble in Lumpy Space"; she kept making things harder for Finn to help Jake by being a Jerkass and when Finn calls her out she says she was only trying to help and makes him feel bad.
The three Jerkass ghosts from "Heat Signature" who spend the whole episode beating up and humiliating F & J, and don't recieve any sort of punishment for their actions.
Karmic Transformation: When Finn becomes a thief. The irony is that he spent the entire episode chastizing and punishing thieves.
Kawaisa: The cute little creatures from "Conquest of Cuteness" even if they don't think of themselves as such at first. The Cute King ends up exploiting his cuteness.
Kissing Warm Up: Referenced in the episode "The Enchiridion." Finn opens the eponymous book to examine it and finds a page titled "Chapter 5: How to Kiss Princesses." Pausing the scene quickly reveals that the author recommends practicing on a Lip Monster beforehand.
Kiss of Death: Subverted. A kiss from Death restores your memories.
"WE GOTTA WAHN DA BEEEEARS!!"
"You BEARS gotta get outta here! Or you're all gonna be MELTED BAH LAVAH!"
"IS PB OKAY?!?!?!?!"
The Earl of Lemongrab.
"This castle is in UNACCEPTAAABBBBLLLLLEEEEE CONDITIIIIOOOOOOONNNNNN! UNACCEPTAAAAAAABBBBLLLLLEEEEEEE!"
Last of His Kind: Word of God has it that Finn thinks he's the last human, although it's uncertain whether he truly is. There are certainly plenty of humanoids, though.
Lady Rainicorn's parents thought humans were extinct before meeting him. They might have the right idea, but it's still ambiguous, since they live in the Crystal Dimension most of the time. On the other hand, since they wanted to eat Finn and they regularly dine on a human-flavored soy substitute, they might be in a position to know about this.
The episode with Susan Strong leaves this ambiguous.
In "Beautopia", it's revealed that Susan is most likely human.
"Holly Jolly Secrets" reveals that the Ice King used to be human as well, and likely lived before the Mushroom Wars
Late Arrival Spoiler: The preview for "Too Young" shows Princess Bubblegum as a thirteen-year-old.
Lava Pit: Beemo's video game Guardians of Sunshine has one.
Level Ate: At least a large portion of the Candy Kingdom is made of... well... candy. The sidewalks are made of peanut brittle and the foliages are made of cotton candy, for example.
Lighter and Softer: The Thanksgiving special "Thank You" takes a radical turn from the rest of the series, being that there is little action, little spoken dialogue and a solid Aesop.
Like-like Confession: In Mortal Recoil, Finn finally admits that he likes Princess Bubblegum "a lot". However, she probably didn't hear it because of being possessed by the Lich. Or maybe she did...
Lotus Eater Machine/Daydream Surprise: In "Power Animal", Finn is trapped in a machine that is powered by thoughts. He breaks out of the machine and finds that Jake has broken into the gnome kingdom where Finn is being held and they tearfully rejoice. Turns out that the machine is actually working and is one of these.
Love Makes You Dumb: So far, Finn's love for the abovementioned Flame Princess really seems to mess up his sense of judgement, even to the point where Finn was having troubles with his heroics versus his love though he agonizes over this.
Luminescent Blush: We dare you to count how many times Finn had this in "The Real You", and for that matter, "Blood Under the Skin".
"You look so cute sitting in your boat, I wanna suck out your eyeballs and rip out your throat. I wanna suck out your eyeballs... and rip out your throat..."
The song she sings in "What Was Missing" also definitely counts:
"Lada-da-da-da, I'm going to bury you in the ground. Lada-da-da-da, I'm going to bury you with my sound. I'm gonna drink the red from your pretty pink face..."
Magic Antidote: In "Trouble in Lumpy Space", antidote for lumpiness isn't in the orb; the orb is the antidote.
Magic Wand: Xergiok has one. According to Finn they are for wiiimps!
Maintain the Lie: The plot for "Her Parents". Jake has to pretend to be a rainicorn to impress Lady's parents, because rainicorns and dogs are supposed to be enemies due to a war. It turns out that her parents don't care that Jake is a dog, because a dog saved Lady's father in the war.
Major Injury Underreaction: Finn's reaction to getting both his legs broken in two places each "No One Can Hear You":
Memetic Hand Gesture: The whole "Adventure Time!" fist pound between Finn and Jake.
Memory Gambit: Finn uses one in "The Real You". In short, Finn was given superhuman intelligence through a pair of nerd glasses. During a science barbecue, he shows off a black hole that threatens to envelop the entire Candy Kingdom. Smart!Finn refuses to stop it, so PB removes them herself. The now-dumb Finn slays the black hole easily with no recollection of his plan, winning PB's heart.
Finn, for harpooning Marceline's touching reconciliation with her father, even though it was awesome.
Also, the Royal Tart Toter in "The Other Tarts", interrupting Finn and Princess Bubblegum's reconciliation hug.
Monster Clown: The clown nurses from "Another Way", who have some sort of foot fetish which they perform onFinn. It doesn't help that he faints and starts having clown nightmares.
As mentioned, Finn slashing and banishing Marceline's dad in the middle of his reconciliation with her daughter.
Happens a little in "Mortal Folly" and "Mortal Recoil": the Lich, Knight of Cerebus that he is, did have a lot of scenes, but there was also a lot of scenes with the Ice King acting goofy and not knowing what's going on, jarring with the scenes of the relatively serious villain.
A good example is in "Morituri Te Salutamus", in which the scenes repeatedly change between Finn violently defeating the ghost-gladiators and Jake happily singing about raising morale. On top of this, the Fight King, like the Lich, is a completely serious villain.
"What Was Missing" starting as a super-silly "write a song" episode. But once Bubblegum calls Marceline's lyrics too distasteful, it becomes a completely serious song where Marceline confesses her feelings about Bubblegum and their past, over a droning electric bass. "I shouldn't have to be the one who makes up with you, so why do I want to?" She backs off once she realizes how confessional she's getting, but DAMN.
Same episode, with Finn's song, which starts out with Finn admitting that he's incredibly self-conscious of the fact that he's younger than all his friends and occasionally questions his friendship with them.
"Holly Jolly Secrets" has this in spades at the end. Silly Ice King antics for the entire episode and then suddenly the Apocalyptic Log of Simon Petrikov turning into the Ice King. Followed immediately by Jake making a joke.
In "Ghost Princess", there is a scene that shows Clarence and Ghost Princess on a date at a Spirit Waves show. When Clarence tells Ghost Princess how beautiful she is, the scene cuts to Finn wildly desecrating graves.
"Just the Way You Are" at the very end. After being followed and copied by a bear for the entirety of the episode, Finn proceeds to tell it off at Jake's behest, causing it to run off into the woods and cry. Luckily, Finn chases after it, and after giving it a heartwarming Be Yourself speech, he hands the bear then Enchiridion, and it merrily goes off on its way (which happens to be straight into the Lich's den, where he delivers the Enchiridion).
In "Dream of Love", the main characters get really brutal towards the relationship of Tree Trunks and Pig and how they don't like it. The one person that has no excuse is Jake who, by Word of God, is boyfriend to Rainicorn and loves romance movies. Yet he doesn't want these two to be together for some reason.
The worst part was there was no real reason their love wouldn't work out. No one's life was in danger, there was no treacherous plot. It was just two people in love and the main cast being dicks.
In the episode "In Your Footsteps", Princess Bubblegum seems to be very happy with the bear posing as Finn giving her the "Heimlich maneuver". She even knew that it was a bear. She should have backhanded him to next Tuesday. Every episode prior to this shows PB shrugging off Finn's romantic advances, saying the age difference is the main problem. Then a bear grabs her from behind and she's okay with that? Unless... she really wants a physical relationship.
Mountain of Food: Downplayed with Everything Burrito, which contains pretty much every common food you can imagine. Yum. Did we mention it also contains pans and cups?
Played literally with the Rock Candy Mountains in the Candy Kingdom.
Mysterious Parent: We don't know who Finn's real parents were, all we know is that Jake's parents were his adopted ones. We also don't know PB's either.
Never Trust a Trailer: The previews for "The Other Tarts" as well as the title card imply that the Royal Tart Toter would have an important role. He didn't. He showed up only at the end of the episode for the sole purpose of being creepy and delivering an Ice Cream Koan.
Happened even worse with "Holly Jolly Secrets". The trailer implied several characters would show up throughout the episode. In reality, only Finn, Jake, and the Ice King had prominent roles.
Nice Hat: Quite common in the series. Finn's hood, the Ice King's crown, and Party Pat's fedora are pretty good examples.
To that, let's add Marceline's sunhat in "What Was Missing".
No Infantile Amnesia: Finn remembers an incident that happened during infancy where he crapped boom-boomed on a leaf and fell backwards into it and no one would help him.
No One Could Survive That: In "The Real You", Finn risks his life by jumping into a black hole. Thankfully, he used his fourth-dimensional sword to make it explode. ...So yeah.
Noir Episode: There is a season four episode called "B-Mo Noire" that will possibly feature this.
Non-Indicative Name: There's a character named Gary the Mermaid Queen in "Witch's Garden". She is an animated human skeleton and acts rather bird-like.
Doctor Princess is not really a princess. "'Princess' is just a surname."
There are many kingdoms in the Land of Ooo, but many of them are ruled by princesses, which would actually make them principalities.
"Holly Jolly Secrets." The only secret revealed in the episode isn't jolly at all.
At the start of "The Jiggler", Finn and Jake have just finished an adventure where they saved a "family" composed of a pair of watermelons, sausages, marshmallows and such (not even anthropomorphic, either), which apparently involved rescuing them from an evil citadel, a lot of fire, and Finn swallowing a little computer at some point.
In "Prisoners of Love", Jake tries to play a flute that immediately breaks. Jake mentions that he broke it when they "unlocked that Sad Ogre's heart", an adventure we have not seen and are not told any further details about.
"Morituri Te Salutamus" begins with the last seconds of an incident that somehow involves a giant burger monster, a pile of cute little hedgehog-like critters, and Jake not sticking to the plan.
In "Holly Jolly Secrets," the first time the Ice King wore his magical crown, he was lost in the resulting visions it made him see, and when he took it off, he only knew that he had done something unforgivable that caused his fiancée to leave him forever.
In "Ghost Princess", some ne'er-do-well ghosts were about to fight Finn and Jake, until Clarence showed up; at which point, this exchange takes place:
Clarence: Hold up! These guys are with me. Ghost: A'ight, Clarence, but only because of that one time when I did that thing by accident, and you were cool about it.
In Hot To Touch, Finn calls Fire Princess innocent, like the steam on a puppy's nose looking for ham in the snow. Jake responds:
Jake: A guy drops one piece of ham in the snow and he never hears the end of it!!
Not Me This Time: One episode has Princess Bubblegum order Finn and Jake to capture the Ice King, even though he objects, claiming to have done "no recent crime." Played With because he did do something, but accidentally.
In "Princess Monster Wife" when Finn and Jake confront the Ice King over the princesses' stolen body parts he says he's not the culprit and he's just as concerned as they are, as the thief might come after his own princess. It turns out this princess is made from the body parts of different princess, he was the culprit and he thought they were talking about another body part thief.
Not Quite Dead: Happens twice with the Lich. The first time, he is defeated by Finn and his sweater, but he body surfs into Princess Bubblegum, who is accidentally dropped into the well of toxins by the Ice King. The second time, while taking control of Princess Bubblegum's body, he is frozen and shattered. No dice. He body surfs again into the waving snail.
We see Me-Mow fall off a cliff after Wildberry Princess' body explodes. Me-Mow somehow hitches a ride on a bluebird, thus preventing a messy end.
Not What It Looks Like: Happens in "Fionna and Cake" when Cake finds Fionna with Prince Gumball in his room in front of his bed with her dress torn.
Off-Model: Many fans complained that Jake was this at the beginning of "Crystals Have Power".
An Offer You Can't Refuse: In "To Cut a Woman's Hair", a tree witch threatens to kill Jake if Finn doesn't get her princess hair.
Official Couple: While Lady Rainicorn and Jake were just flirting cutely in the pilot, in the series, they're officially dating.
Offscreen Moment of Awesome: The epic battle between the Lich and Billy for the fate of the world. All we saw was the brief snippet in Billy's Song, which consisted of Billy kicking the Lich into his castle. Considering the Lich ultimately ended up in the Candy Kingdom being pummeled into a tree so hard he was sealed in amber (which we don't see either), it's clear the rest of the battle was likely extremely awesome.
Finn, Jake and the Ice King's ninja fight in "The Chamber of Frozen Blades".
Off with His Head: Finn does this a lot in "Morituri Te Salutamus" to the gladiator ghosts.
A Lich-possessed Princess Bubblegum does this once the Lich regains his true power. He's powerful enough that he beats the tar out of Finn, Jake, and the Gumball Guardians of the Candy Kingdom with no effort, requiring an Enemy Mine with Ice King.
He wasn't at full power yet. He was planning to regain it after he wrecked the Candy Kingdom.
Oscar Bait: The season three episode "Thank You" was deemed "Oscar-worthy" by Cartoon Network, so they put a preview of the episode in a movie theater so that it could qualify.
Overly Long Title: The upcoming video game is titled Adventure Time: Hey Ice King! Why’d you steal our garbage?!
Owl Be Damned: The Cosmic Owl at the end of the Croak Dream. This refers to the fact that many religions see the owl as an omen of death to come.
Paper-Thin Disguise: Finn, Jake, and Tree Trunks' disguises in "Apple Thief" (if they can even be called that). They just cover themselves in dirt, and the bartender that they met not 30 seconds ago doesn't even recognize them.
Playing Sick: In the original storyboard for "Storytelling" Jake is not really sick. He only does says so in order to make Finn leave so that he could stay at home doing weird things while no one was looking.
Poor Communication Kills: In "What Have You Done?" because Bubblegum doesn't adequately explain what the Ice King did and just says he "didn't do anything" Finn thinks he's going to be punished for no reason and sets him free.
The Power of Friendship: How the gang opens the door in "What Was Missing", along with the power of honesty.
Literally with the Business Men. They even have a main mook with a different colored tie to tell who's the King Mook and who are regular Mooks.
The Crystal Men in "Crystals Have Power," who are somewhat awkward about the whole thing, say they're just following orders, and have to keep themselves from getting distracted and texting.
Scorcher seems to qualify as well, the moment his business is done, he just leaves without any further fighting.
Gate guard: [Why] did you die? Finn and Jake: ...Because we're awesome!
The Quiet One: Scorcher, a hitman Ice King hires in "Hitman".
(Scorcher appears behind Ice King) Ice King: Whoa, you are fast. (beat) Ice King: And quiet. (beat) Ice King: And very good at dramatic silence, I like it...
Raised by Humans: At one point, Finn The Human tries to raise a baby Jiggler. His heart's in the right place, but he doesn't know how to take care of the Jiggler and nearly kills it. He ends up bringing the baby back to its mother.
Raised by Wolves: "Memories of Boom Boom Mountain" reveals Finn was abandoned as a baby and adopted by Jake's parents.
Rapid-Fire "No": Finn delivers one in "The Chamber of Frozen Blades".
Finn also does one in "Hot to the Touch" after Flame Princess accuses Finn of having crying as a power.
Rapunzel Hair: Princess Bubblegum, Marceline and Finn have really long hair.
Reality Warper: Anything Jake imagines becomes real, for some reason. Finn eventually repeats the effect.
"The Reason You Suck" Speech: A very blunt one given by Finn to the Tree Witch in "To Cut a Woman's Hair", with Jake continuously and angrily shouting, "DUUUDE!"
Finn: If there's anything I've learned today, it's that I am awesome at talking to ladies. And lady, you are CRAZY UGLY! Having beautiful hair isn't gonna get you anywhere because you're ugly inside and out. So ugly, I want to throw up. No one will ever find you beautiful. EVEEERRR. And it has nothing to do with the old chrome-dome. (touches his heart) It has to do with what's in here.
Retired Badass: Billy. How Badass was he? He killed an evil ocean... by PUNCHING IT! Still not sure? Princess Bubblegum says Billy didn't just imprison the Lich in amber, he did so by pummeling him into the tree.
Retractable Weapon: Fionna's crystal sword even though it turns out to be a trap.
Reset Button: Princess Bubblegum becoming 18 again in "Too Young."
Royals Who Actually Do Something: In one episode, Finn becomes king of a goblin city. He tries to be this, but the rules of the city force him to essentially be a figurehead.
Princess Bubblegum probably counts, as she actively worked to fix the plague the Ice King accidentally caused and betters her kingdom through her scientific research.
RPG Elements: Levels, cursed objects you can't take off etc. More DnD-style than video games, and tends to only be minor elements that are only important for the episode.
