1. The original stand-alone short was commissioned by Nickelodeon's Random! Cartoons. It leaked online before it aired in 2008 and went crazy viral.
2. Though that original pilot did air on Nickelodeon, the network turned down the series twice.
3. Creator Pendleton Ward worked as a storyboard artist and writer for Cartoon Network's similarly bizarre The Marvelous Misadventures of Flapjack before Adventure Time got the green light.
4. He cites My Neighbor Totoro, The Simpsons, and Pee-Wee's Playhouse as stylistic influences.
5. But the romance is inspired by Archie comics' Betty and Veronica.
6. His favorite character is BMO.
7. And his beard has a Facebook page.
8. Ward voices Lumpy Space Princess, whom, he says, he's "embarrassed at how much [he] relates to."
9. Olivia Olson, who voices Marceline, was the little girl who sang "All I Want For Christmas Is You" in Love Actually.
10. Tom Kenny, who voices the Ice King, also voiced Spongebob Squarepants. (And Heffer on Rocko's Modern Life, and the Mayor on Powerpuff Girls. His voice is everywhere.)
11. Hynden Walch, who voices Princess Bubblegum, is also the voice of Starfire in Teen Titans.
12. Jeremy Shada, who voices Finn, raps in his spare time. Here's a song about him running errands with his mom.
13. Neil Patrick Harris voiced Prince Gumball.
14. George Takei voiced Ricardio the Heart Guy.
15. Rainn Wilson voiced Rattleballs.
16. Lena Dunhman voiced Betty Grof.
17. Andy Samberg voiced Party Pat, who is based off former creative director Pat McHale.
18. Lady Rainicorn speaks Korean, and translations can be found here.
19. In the Korean dub, she speaks English.
20. She and BMO are both voiced by Niki Yang.
21. But Pendleton Ward voiced her universal translator device.
22. In "My Two Favorite People" (S01E09), the "joke" she makes is actually just a memory of the time she and Jake ran naked through an orchard and ate all of the farmer's apples.
23. And in "From Bad To Worse" (S03E13), when Jake apologizes for biting her, she responds, "I wanted you to bite me." Lady Rainicorn is sassy.
24. Jake and Finn's parents are named Margaret and Joshua.
25. Finn's name was originally "Pen," after Pendleton Ward, but Ward allegedly changed it because he "didn't want to see his name on the back of sweatjeans."
26. And Princess Bubblegum was originally named "Bettie" after Ward's mother.
27. Her name is now Bonnibel, which only Marceline has called her.
28. Princess Bubblegum can alter her age by adding or subtracting candy biomass.
29. In the video game "Adventure Time: Explore the Dungeon Because I DON'T KNOW!," she reveals that she gestated in a "sentient pink soup" a thousand years ago. The game also says she is 827 years old.
30. And she can speak German, as seen in episodes "What Have You Done?," "Go With Me," and "Frost & Fire." In the German dubs, she can also speak Turkish.
31. Marceline is the only main character who didn't appear in the original short.
32. She has four bass guitars (the original, red, four-string Fender 1951 Precision Bass; the family heirloom Ax Bass; the Butterfly Bass, which she's yet to be seen playing, and the Devil Monster Bass, which she got as a gift from Wizard Bill) and one banjolele, which stays in the Nightosphere.
33. The heartbreaking Simon and Marcy backstory came from the fact that Ice King sang Marceline's Fry Song in "Holly Jolly Secrets" and realized they needed an explanation for why the two had never really interacted before.
34. And the implied romantic backstory between Marceline and Princess Bubblegum in "What Was Missing" (S03E10) was the source of major controversy. The official YouTube channel even published a recap that said, "Marceline hints that she might like Princess Bubblegum more than she'd like to admit." The preview video was pulled by Frederator Studios, who produces the show, but the episode is still aired in reruns.
35. "I'm Just Your Problem," Marceline's song from "What was Missing", was based on a real life falling-out writer and composer Rebecca Sugar experienced.
36. Finn has deuteranomaly (where he sees red as green), seen when he mistakes an emerald for a ruby in "Red Starved" (S05E38).
37. And he's ambidextrous, along with Marceline.
38. In the pilot, Finn was voiced by Jeremy Shada's older brother, Zack.
39. Unlike in most cartoons, Finn actually ages as the show progresses, so his voice actor, Jeremy Shada, can keep voicing him. At the start of the series, he is 12 years old; as of season six, he's 16.
40. To show that Finn was going through puberty, Jeremy Shada would purposefully crack his voice.
41. Pendleton Ward cites Bill Murray's character from Meatballs as the main inspiration behind Jake's personality. He describes Jake as "a 20-something year old dude who gives this crappy advice."
42. In the original short, Jake is 28 years old.
43. Jake's insides were cursed to smell like vanilla, as revealed in "The Silent King" (S02E14).
44. And he's died once in the series, in "Sons of Mars" (S04E15).
45. John DiMaggio, who voices Jake, also voices Bender on Futurama.
46. This made it especially exciting when Finn and Jake appeared in Futurama (in "Leela and the Genestalk"). Bender meets them locked up in a dungeon.
47. The gender-reversal in "Fionna and Cake" (S03E09) is a common sci-fi/fantasy trope called "Rule 63," which states that for every given male character, there is a female version of that character, and vice versa.
48. Fionna wears a Sailor Moon dress to Prince Gumball's party.
49. The only character who didn't change in the Rule 63 universe is BMO, who alternates her gender regularly.
50. And if one episode just wasn't enough, you can follow Fionna and Cake in their own comic book run.
51. Adventure Time's female characters are so kickass because Pendleton Ward doesn't let them stray into obvious caricatures. He told io9, "[T]here's so many stereotypical girl characters, and the easiest thing to do is the opposite: girl power, making them extremely intelligent or extremely tough. I just want to make girls that are normal, just like Finn is normal." What a concept!
52. The show is heavily censored in Australia for possible sexual innuendo. In "Memories of Boom Boom Mountain" the line, "No, it's raunchy and maddening! All those men and their disgusting, fantastic bodies!" got cut to just "No!," which is a bummer for that audience.
53. The cast records all their dialogue in one room, which is rare for an animated show.
54. There's a hidden waving snail in every episode.
55. A Bacon Pancakes / "Empire State of Mind" mashup exists and it is the best thing in the whole wide world. John DiMaggio, who voices Jake, named it as one of his favorite fan creations.
56. Flame Princess is the only princess to have invaded an entire kingdom by herself.
57. The episode "Memory of a Memory" (S03E03) was partially inspired by Eternal Sunshine of the Spotless Mind.
58. And "Gotcha!" (S04E12), in which Lumpy Space Princess goes undercover to write a book, was partially inspired by the made-for-TV Hilary Duff movie Beauty & the Briefcase.
59. Lumpy Space Princess is made from irradiated stardust.
60. Ice King has a tattoo of a penguin on his right butt-cheek, as seen in "Prisoners of Love" (S01E03).
61. The writers of Adventure Time play writers' games where everyone has two minutes to draw a picture, and the person next to them has two minutes to write the first act. Out of all 30 to 40 results, maybe one will make it into a full episode.
62. Pendleton Ward has compared the writing process to playing Dungeons & Dragons, saying, "[A]t the beginning, when we didn't have any time to play Dungeons & Dragons anymore because we were all working so hard on the show, we realized, 'Well, we can still play sort of, just by writing the stories we'd want to be playing D&D with.'"
63. One side project Pendleton Ward would like to see developed: a real-life version of Card Wars, the augmented-reality card game Finn and Jake play in the episode of the same name (S04E14). He told Fast Co. Create, "You stick an image in front of a camera, and the camera can register what the image is and project it on the TV screen. You'd see the cards and see something projected out of the card. Which sounds awesome to me. it would be fun to do something like that." Make it happen, people.
64. It takes about nine months to make one episode, but production for each episode overlaps, thank GOODNESS.
65. Most of the jokes or gags that get nixed by the network are fart-based.
Marceline's last name is Abadeer, not Aberdeen, as previously stated in the post. Also, the Bacon Pancakes mashup is with "Empire State of Mind" not "New York State of Mind" though an Adventure Time / Billy Joel mashup would probably be great, too, if anyone wants to get on it. H/t to Talia, Cameron, and ATaranto in the comments.