Adventure Time/Shout-Out

In the original short Finn mentally projects himself to Mars.
One promo after "Freak City" has the double rainbow video recreated with Jake witnessing two Rainicorns.
Marceline calls Finn a Castle Crasher in her second episode.
In "The Duke", one of the potions Finn and Jake are messing around with is labeled "Caturday Surprise."
Billy's sword is called Nothung, the name of Siegfried's sword in Der Ring Des Nibelungen.
The title card of "His Hero" is a nod to Frank Frazetta's Death Dealer.
Finn's plastic surgery turns Lumpy Space Princess into a Gizmoduck lookalike.
After being freed from prison, the Ice King loudly proclaims "CAST DETECT SECRET DOORS!" before blasting a hole to freedom.
- Mind you that happens in a room that has been proven to have at least 2 real hidden doors.
The horse in "The Eyes" is based on the Fat Shetland Pony from Hark! A Vagrant.
The Ice King has a "Ring, Ring, Ring, Ring, banana phone"
The series title card is styled after the Dungeons & Dragons 3rd Edition logo and the cover art of the game Another World.
The episode "Guardians of the Sunshine" is FULL of reference to video games.
- It uses sound effects from many games, particulary Mega Man.
- It also makes a few Super Mario Brothers references, like level-1, and the Bomba (Bob-omb).
- Finn's face turns into pong at one point.
The zombie Sugar Person in "Slumber Party Panic" tells Princess Bubblegum to "Gimme some sugar, baby."
The episode "Dungeon" featured a number of DnD monsters, such as the mimic, the trapper (pretends to be the floor), and a gelatinous cube.
- And "Wizard Battle" has a brief cameo by a classic Carrion Crawler.
In "My Two Favorite People", Finn, Jake, and Lady Rainicorn encounter a wizard who is handing out power rings. Finn also wears 10 rings his hands with each one displaying a different power, just like the Iron Man villain The Mandarin.
According to Natasha Allegri's Formspring^{[dead link]}, Fionna and Cake are based on a certain planet-themed magical warrior girl and her talking black cat. The rabbit hat is a dead giveaway.
- The dress Fionna wears in the episode is another Shout-Out to Sailor Moon.
The robot orb-looking things that Fionna slashes at in "Adventure Time with Fionna and Cake" were based on the farm-intruding enemies from The Legend of Zelda: Majora's Mask.
The episode Mortal Recoil contains a bunch of clear references to The Exorcist and The Grudge.
The tagline for the movie "Heat Signature" is "Under the ocean, no one can hear you die". This is a reference to the tagline for the movie Alien (1979): "In space, no one can hear you scream."
- The look and Calling Your Attacks nature of the "Vampire Kick" may be a reference to Kamen Rider.
In "Morituri Te Salutamus" just before one of the fighters dies, he says something along the lines of, "Et tu, Verus?" which is a reference to Julius Caesar.
The "Susan Strong" title card is a reference to Lost. There was also a "Lost pan" in the storyboard that got cut from the episode.
- Not to mention how Susan Strong & Co also lived underneath a Hatch...
- One of the fish people is wearing what looks like a Pedo Bear costume.
The title card for The Enchiridion! was inspired by a Science Fiction magazine cover.
Ash erasing Marceline's memory of her breaking up with him was slightly inspired by Eternal Sunshine of the Spotless Mind.
- The entire memory sequence is a reference to Being John Malkovich, what with the shifting gravity, various doors through memories, and nature of being inside someone's head.
- It can also be seen as a refrence to Inception with the extraction of an idea from a dream.
- Jake's Giant Foot of Stomping is, of course, a reference to Monty Python's Flying Circus.
The Lich King, a horned, ridiculously scary, skull-faced monarch who can raise skeletons and whose power lies in a pit of green ooze. The Horned King, a horned, ridiculously scary, skull-faced monarch who can raise skeletons and whose power lies in a pit of green ooze. Welp.
The game Dropball, played by Ghost Man in "Blood Under The Skin," is a Shout-Out to Bullet Ball, the high calibre tablegame designed for the 21st-century lifestyle that went memetic after creator Marc Griffin's memetically depressing/hilarious appearance on American Inventor. Ghost Man's voice sounds quite a bit like Marc Griffin's and several of his lines are quotes from the American Inventor episode.
Finn's method of curing the zombies in "From Bad To Worse" is to douse himself with the antidote and walk into a mob of them so they all touch him.
The title card for Beautopia^{[dead link]} references the famous Greetings From Asbury Park, N.J. postcard.
The episode "No One Can Hear You", references Alien when the candy people are shown to be stuck to the walls of the sewer with a goo, like the Xenomorphs do the their victims. Even the title is borrowed from the Tagline of the movie: "In space, no one can hear you scream." Bonus Points for Finn and Jake screaming in the title card.
- On the opposite end of the spectrum, Finn's casts breaking is really similar to Forrest Gump's leg braces.
The crew made an episode in honor of a little kid and his drawing of her original character, Me-mow, fighting Jake, which he titled "Jake vs. Me-mow".^{[dead link]} Appropriately, the episode is called "Jake vs. Me-mow".
- The music box Finn uses to accompany the lullaby is strongly similar to the Orb of Isis in The Simpsons episode "Lost Our Lisa."
The Bucket Knight is a shout-out to the Alternian Imperial Drones from Homestuck. The artists are confirmed to be fans: a picture of their whiteboard shows doodles of the main characters.
From "Paper Pete" we have: "YISS!!"
"Partake of the fruit..."
The first issue of the comic shows a cross-section of the ground... including a fossilized T. rex about to stomp on a house.
The episode "Wizard Battle", the Grand Wizard states that wizards will fight using the eight schools of magic. This is likely a reference to Dungeons & Dragons' eight schools of magic.
"Five Short Graybles" has Princess Bubblegum making a familiar toothy smile while enthusiastically saying "CHEEEESE".
"Princess Monster Wife" alludes to Perseus and Medusa when Finn and Jake use mirrors in order not to gaze upon the titular monster's hideousness directly, though they are only in danger of fainting instead of being turned into stone.
The internet game "Rhythm Heroes" is clearly a parody of Rhythm Heaven.