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The Best Adventure Time Episodes To Watch During Halloween

"Adventure Time" is no stranger to horror. From episodes that are full-on homages to celebrated scary movies to the presence of Marceline, vampire queen and heir to the throne of the demonic Nightosphere, all things spooky appear within the celebrated cartoon's 10-season run. This makes "Adventure Time" an ideal Halloween watch. But with so many episodes to choose from, how is a prospective fan supposed to know which are the absolute spookiest?

We decided to comb through the entire series to answer this question ourselves. Some of these episodes are truly scary, while others are focused on creepy-but-sweet characters. A few recreate classic horror movies with a clever cartoon twist. Each and every one of them is a joy to watch — especially with a bowl full of candy. Embark upon a trip to Ooo for some frightening fun with this list of the best "Adventure Time" episodes to watch during Halloween.

Slumber Party Panic (Season 1, Episode 1)

The first-ever episode of "Adventure Time" is full of details you might not have noticed if you've never revisited it. It begins when Princess Bubblegum tests out a "decorpsinator serum" she's created. The serum is meant to bring dead candy people back to life, but it actually resurrects them as undead zombies who want to feast on sugar (which, as their name suggests, candy people are made of). Princess Bubblegum calls her sweet subjects together for an impromptu slumber party, and commands Finn to keep the undead away. She further orders him to make a "royal promise" not to tell anyone what's actually going on, because candy people explode when they get scared.

This episode squeezes a huge number of plot points into 11 minutes. Finn is forced to become creative in his efforts to simultaneously keep the candy people safe from the zombies and keep them ignorant of the truth. All the while, Jake tries to get Finn to spill the beans. When he finally does, Finn must face the spacetime-disrupting consequences of breaking a royal promise. This homage to classic zombie flicks isn't just fun, it's outright impressive. What other cartoon comes out of the gate with a horror story starring talking dogs and adorable candy people?

Henchman (Season 1, Episode 22)

"Henchman" begins when Finn sees Marceline arguing with an old man who swore to serve her for life. Affable Finn offers to take the old man's place as her henchman, which horrifies vampire-wary Jake. He vows to save Finn from Marceline — but as it turns out, Finn doesn't need much saving.

This episode is a series of vignettes, in which Marceline commands Finn to do things that sound nefarious and scary, but end up being harmless. He has to hold down a widowed pianist, so that Marceline can feed ... on his huge red bow tie, because she devours the color red, rather than actual blood. He has to lead an army of necromanced skeletons to the castle of the Duke and Duchess of Nuts ... only to discover that Marceline and her army are welcome guests at a birthday party. He has to chop down an adorable young dimple plant ... so that it doesn't grow into a carnivorous monster. All the while, Jake is close behind, but can't quite bring himself to attempt a rescue. "Henchman" delivers real tension, some truly scary monsters, and a large dose of humor, which keeps things from being too creepy.

It Came from the Nightosphere (Season 2, Episode 1)

"It Came from the Nightosphere" begins with Finn and Marceline having a jam session. After Marceline sings a moody song about her dad stealing her fries, Finn is eager to help father and daughter reconcile. One quick and creepy ritual later, Hunson Abadeer, Lord of the Nightosphere and Marceline's dad, arrives.

Ever the bad guy, Hunson immediately begins a terrifying, soul-sucking tour across Ooo. But before he leaves, he takes Marceline's bass, which we learn is a family axe (like, a literal axe) that Marcy has refashioned into an instrument. Finn and Marceline set off to stop Hunson, though Marceline is mostly interested in getting her bass back. 

"It Came from the Nightosphere" does a perfect job of introducing Hunson Abadeer, who is equally invested in evil and being a good dad, even though he has a hard time with the latter gig. The episode also offers a number of nicely scary moments, a surprisingly catchy song about sucking ants' souls, Marceline's iconic french fry lament, and a genuinely sweet resolution.

The Eyes (Season 2, Episode 2)

"The Eyes" is one of the creepiest and funniest episodes of "Adventure Time." The plot is incredibly simple: There's a horse on a hill near the treehouse that won't stop staring at Finn and Jake while they try to fall asleep. Our heroes repeatedly try to get the horse to leave them alone, or at least get it out of sight, to no avail.

They begin by simply closing the blinds, which leads to a visual gag in which the moon lights the horse from behind, creating a sinister silhouette. Frustrated, they go out to meet the horse. They ask it to leave, but it simply widens its pupils. Jake grows big and moves it far away, but it rushes back to the hill. Jake then attempts to lure it away by playing some music, but this plan hilariously backfires by luring a group of snakes instead. These attempts go on for a while, and eventually, Jake claims the horse has "whacked-out poo brain." This diagnosis comes up a number of times throughout the episode in increasingly funny exchanges. This is a wonderfully simple episode that boasts a serious spook factor and some of the funniest jokes in the show.

Death in Bloom (Season 2, Episode 17)

"Death in Bloom" brings Finn and Jake to the literal land of the dead. After they accidentally kill the princess plant Princess Bubblegum asked them to keep alive, Peppermint Butler offers to open a portal to the land of the dead, so that they might retrieve its soul. He also asks that they say "hi" to Death for him.

The land of the dead contains many spooky obstacles, from skeletons who want to take Finn and Jake's flesh to a river that wipes the drinker's memory. Their final test comes from Death himself, who informs Finn, "To get stuff from me, you have to beat me in a musical battle." He proceeds to unleash a killer death metal jam. Things don't look great for Finn and Jake, until Finn remembers to tell Death that Peppermint Butler says hi. Death immediately becomes super friendly, as they're friends of a friend. He proceeds to help them get back to Ooo, just in time to meet Princess Bubblegum with her restored princess plant. The episode ends with Peppermint Butler telling Finn and Jake that the price for transporting them to the land of the dead will be their flesh.

"Death in Bloom" offers an eerie journey through the afterlife, and the introduction of Peppermint Butler's occult leanings. This makes it a perfect episode to watch during spooky season.

Mortal Folly and Mortal Recoil (Season 2, Episodes 25 and 26)

"Mortal Folly" and "Mortal Recoil" introduce the Lich, one of the most important and frightening villains in the series. The Lich is the embodiment of the death of all things. In case that concept is too abstract for little ones to grasp, the Lich is also terrifying to look at: A skeletal figure in a large robe, he has hollow eye sockets, ragged skin, and goat horns, one of which is broken off. "Mortal Folly" focuses on the Lich's destructive powers. It's a seriously scary episode, and not just because of the surprising intensity of the violence on display: The sense of danger here is intense and completely real. You really do believe the Lich will be the end of all life on Ooo, and perhaps beyond.

"Mortal Recoil" is a lot more fun. At the end of "Mortal Folly," the Ice King accidentally drops Princess Bubblegum into the Lich's well of power. In "Mortal Recoil," we discover she's become possessed by the Lich. This possession is largely played for laughs, and full of references to "The Exorcist" (and every other exorcism movie). Bubblegum's skin changes color and her voice transforms into the Lich's, but Finn resolutely ignores these developments — he desperately wants to believe she's recovering just fine.

No One Can Hear You (Season 3, Episode 15)

There aren't any vampires, skeletons, or ghosts in this episode, yet it's one of the most truly unnerving installments of "Adventure Time." It opens on a dramatic but brief fight, as Finn and Jake take on a deer that has been licking candy people. Finn is badly injured and gets knocked out. When he wakes up, he appears to be entirely alone in the kingdom. He calls out for Jake, Princess Bubblegum, and eventually anyone at all, but gets no response.

A little later on, he finds Jake, who has sustained a significant head wound. Jake informs him that all the candy people have disappeared because they're throwing him a surprise party. Soon enough, however, Jake reveals he's been waiting six months for the candy people to throw the party. Finn realizes Jake has lost his mind, and that something has gone terribly wrong.

This episode's atmosphere of dread rivals the best horror movies. It also boasts a couple of chilling references to the classic "Alien" franchise, one of which is the episode's title. To top it all off, this episode also gave us what has become one of the most widespread and troubling GIFs on the internet.

Hug Wolf (Season 4, Episode 8)

"Hug Wolf" offers a simple twist on the classic werewolf story: What if, instead of becoming mindlessly vicious wolves, people transformed into mindlessly hugging wolves under the light of the full moon? While on an adventure on a moonlit night, Finn is hugged by a giant wolf creature. When Finn and Jake return home, Finn can't stop hugging BMO so tightly it causes pain. Upon discovering Finn has a fever, Jake sends him to bed. The next day, Cinnamon Bun tells Finn that he can't take any more hugs, but Finn doesn't remember even seeing Cinnamon Bun the night before. This leads Jake to investigate. He promptly learns about "hug wolves" in the library, and that no cure yet exists for this affliction.

This is a very cute episode that has a ton of fun with classic werewolf tropes. One of the most memorable instances of this arrives when Finn allows himself to be chained, so that if he does transform, he'll be unable to hug people. Of course, he wakes up the next morning in a strange place, with no recollection of the night before. It's not a particularly scary episode, but as an homage to werewolf tales, it fits right into the Halloween season.

Ghost Fly (Season 6, Episode 17)

"Ghost Fly" begins with a simple, everyday action: Jake kills a fly. Unfortunately, that fly returns as a ghost. Finn, Jake, and BMO first attempt to escape the ghost fly, but given its ability to move through walls, this doesn't work. They then call Peppermint Butler, who arrives in a shot mimicking Father Merrin standing outside the MacNeil house in "The Exorcist." Pep But draws a protective chalk circle around Finn, Jake, and BMO, and explains his plan to banish the ghost fly using tools he brought with him. Unfortunately, the ghost steals his bag and zooms off. 

The next morning, Finn theorizes that they should be able to extend the chalk circle that kept them safe overnight. But this goes very wrong, and Finn is soon possessed by the ghost fly. He proceeds to transform into a creature out of "The Fly" movies. With its ultra-creepy premise and fun references to classic horror flicks, "Ghost Fly" is one of the very best Halloween-appropriate episodes of "Adventure Time."

Varmints (Season 7, Episode 2)

"Varmints" is one of the few episodes of "Adventure Time" that focuses on characters other than Finn and Jake. Here, we follow Princess Bubblegum and Marceline as they go on an adventure through the tunnels around PB's cabin to rid the area of varmints. The episode plays out a bit like "Aliens," as the pair has to fight back a horde of the creatures, including a giant queen. Beyond this homage, "Varmints" also features some of Marceline's best and scariest transformations, which in this case are also useful in destroying the nasty critters.

This episode is one of the few on this list that may be better suited to dedicated fans of the show, rather than those who simply want to enjoy a spooky installment. During their varmint-busting adventure, Marceline and Princess Bubblegum discuss their shared past and discover new things about each other and their relationship. This conversation makes "Varmints" one of the most important episodes in the entire series, as well as one of the spookiest.

Stakes (Season 7, Episodes 6 - 13)

The "Stakes" miniseries is an "Adventure Time" high point by any metric. The first of three miniseries the show embarks upon in its later seasons, it remains the best of them. Things kick off when Marceline asks Princess Bubblegum to remove her vampirism. PB obliges, but "curing" Marcy releases the vampires whose souls Marceline sucked earlier in her life. Many of the miniseries' episodes focus on these vampires, all of whom have specific powers and abilities. Marceline, Princess Bubblegum, Finn, and Jake are tasked with hunting them down, with the research support of Peppermint Butler. As you might expect, the miniseries plays out a lot like "Buffy the Vampire Slayer," but with "Adventure Time" characters — essentially, television perfection.

Like "Varmints," "Stakes" develops the relationship between Princess Bubblegum and Marceline, which leads to an incredibly sweet moment in which Marceline thanks Bubblegum for "helping [her] grow up." There are plenty of comedic moments as well: Jake continues to grapple with his fear of vampires to hilarious effect, and Peppermint Butler frets over how he'll ask the resurrected Vampire King for his autograph.

Blank-Eyed Girl (Season 7, Episode 19)

"Blank-Eyed Girl" begins with Finn and Jake at a pizza shop, where they hear Starchy reporting on mysterious blank-eyed girls who have been spotted around Ooo. A spooked Jake claims this is nonsense, but on their way home through the dark woods, our heroes hear the snapping of twigs and run all the way home. Once there, they hear a knock on the door. They open it to discover a blank-eyed girl, standing right outside.

The episode escalates from there, with the blank-eyed girls multiplying and eventually entering the treehouse. During these increasingly scary (and silly) incidents, Finn calls in to Starchy's show to try to figure out what kind of creatures the blank-eyed girls are, and how to combat them. The answer is fascinating and frightening in a very unique way. With their hollow eyes, pale skin, grey clothes, and long black hair, the blank-eyed girls look a bit like cute versions of Sadako from horror classic "The Ring." Beyond this visual reference, the episode's mysterious plot also makes it feel like a love letter to the scariest Japanese horror movies of the late 1990s and early 2000s.

Marcy & Hunson (Season 10, Episode 7)

As you can guess from the title, "Marcy & Hunson" focuses on Marceline and her father, Hunson Abadeer. This episode's much less scary than "It Came from the Nightosphere," however, as Peppermint Butler binds Hunson with a spell so that he's unable to suck souls. Thus contained, he attends a concert that Marceline is putting on for a group of ghosts at a cemetery. Hunson cheers loudly for his daughter, and pushes a bunch of ghosts out of the way so that he can get to the front. Marceline is embarrassed, and decides, along with Finn, that she needs to protect her powerless dad. The episode ends up being surprisingly sweet, for something about a soul-sucking demon — Hunson really just wants his daughter to know how proud of her he is.

With its cemetery setting and ghostly cast, "Marcy & Hunson" is great for Halloween viewing. But it's also significantly less scary than many other episodes on this list, making it a perfect choice for those who want to enjoy something eerie, but not explicitly horrific.

The First Investigation (Season 10, Episode 8)

Though "Adventure Time" boasts many wild science fiction elements and a love of horror, these two aspects of the show don't mix very often. "The First Investigation" is one of the only instances of overlap, and one of the best. Jake's son Kim Kil Whan buys Finn and Jake's parents' old investigative offices, and sends an employee to check on the property. The employee returns shaking and unable to speak. Kim Kil Whan then asks Finn and Jake to check out the place. Thinking they might encounter their parents' ghosts, they happily accept the challenge.

When they arrive at the office, they find creepy goings-on and an old videotape. It turns out to have been made by their parents, who wanted to document the space's paranormal happenings. Soon enough, Finn discovers that the office's strange inhabitants aren't spectral, but temporal. He dubs the spooky beings "time slips." We go on to learn that it was Jake, in a panic about what he thought were ghosts, who slipped back in time, terrifying Kim Kil Whan's employee.

Along with being a scary and funny episode, "The First Investigation" is also beautifully emotional. Finn and Jake are able to see younger versions of themselves and their parents, and send them a message of love through time.