Animated short

The original Adventure Time animated short (itself titled "Adventure Time") was originally created as part of Frederator Studios' ''Random! Cartoons'' on Nicktoons Network. Note that while some sources give an official airdate of December 7, 2008, the short actually was made in 2006 and became an internet viral video in 2007.

Synopsis
Princess Bubblegum is captured by the Ice King, and it's now up to Pen (Finn) and Jake to save her.

Plot
(Note: In the original short, Finn is named Pen.)

Pen is sleeping under a tree in a sleeping bag when he wakes up and asks Jake what he's doing. Jake tells Pen he is meditating to connect his mind to the internet. Then he shows Pen a dance he "downloaded." Just then, Princess Bubblegum's rainicorn, Lady Rainicorn, flies by crying. Jake grows and the two follow Rainicorn. Pen tells her a joke to cheer her up, but it turns into a failure and she just keeps on crying.

They follow her into the Ice Kingdom where Ice King starts shooting at Lady Rainicorn with frozen lightning bolts. Pen says that Ice King is an oxymoron and Jake shrinks. Jake sees that Ice King has trapped Princess Bubblegum. After Pen puts on a turtle-neck sweater, he asks Jake if he wants his booties and gives them to him. Pen and Jake yell "Adventure Time!," then jump, slide onto the ice and surf on Penguins. They land into the ice, but they spotted an Iceclops. After they throw snowballs at it, they spot a Snow Golem and they throw snowballs at it as well. Then they see a Fire Elemental who asks for directions to the sun. Pen gives the directions, then throws a snowball at the Elemental. This makes him upset so he asks how old they are. Pen says that he's twelve and Jake says he's twenty-eight.

They then hear an evil laugh and they look up to see Ice King. Jake stretches his legs to boost Pen up to Ice King. Pen tells him to stop it and Ice King tells him to stop meddling and that Pen and his dog can't harm him. Pen says that Jake is not his dog but his friend, and then kicks Ice King into his house and cave, where there was a drum set and a pair of underwear. They kung fu fight as Jake flirts with Rainicorn. Pen asks Ice King why he's always stealing ladies. Ice Kings replies that he's going to make one marry him. Pen says that the king's idea is stupid, and Ice King says Pen's hat is stupid. Pen gets mad and kicks him in the face as he screams the highly known words: "My hat is AWESOME!!!." Then he realizes that Jake is not helping him, so he looks out to see him talking to the Rainicorn.

Ice King uses his frozen lightning bolts to freeze Pen in a block of ice. Then, his mind gets transported back in time and onto Mars, where he meets Abraham Lincoln. Lincoln tells Pen that he needs to believe in himself. Pen screams "NEVER!!!" as his mind is transported back to the present and breaks out of the ice block. He sees Ice King fly away with Princess Bubblegum who yells for them to help her. Rainicorn, Pen, and Jake chase after Ice King. Pen jumps and grabs the princess as they land on Rainicorn. Then Jake knocks the crown off of Ice King's head and Ice King falls to the ground. Jake walks away on his outstretched legs.

Pen and the princess land as Pen tells her that she is free. The princess kisses and thanks Pen. Jake comes and asks what is going on and Pen says nothing is. Embarrassed, Pen drags Jake away and says that they have stuff to do. Jake denies it and says that they have nowhere to go. Pen laughs and says that "adventure awaits."Jake says that he doesn't see an adventure going on anywhere and that they should just sit there and talk about their feelings. Pen randomly points at three Ninjas stealing an Old Man's diamonds. He says bye to the princess and the princess bids farewell. Pen and Jake say it's "Adventure Time" again and they run off.

Main characters

 * Pen
 * Jake
 * Princess Bubblegum
 * Ice King.

Minor characters

 * Abraham Lincoln
 * Iceclops
 * Snow Golem
 * Fire Elemental
 * Ninjas
 * Old Man
 * Penguins
 * Lady Rainicorn

Trivia

 * The show has made references to this short in various episodes, like Abe Lincoln on Mars.
 * Pen (aka Finn) is named after series creator Pendleton Ward, is 12 years old, and does not live in his usual tree house in this pilot; he sleeps under a normal tree.
 * Lady Rainicorn speaks by cooing like a dove instead of talking Korean.
 * All of the voice actors in this pilot are different from the actors who performed voices in the series, aside from the actors for Jake and Abraham Lincoln.
 * Recently, lead character designer Andy Ristaino confirmed that the short was non-canonical.
 * The title card resembles the title screen in the opening sequence of the series, except that Pen (aka Finn) has his hand on his forehead instead of in the air, and Jake is on his left instead on his right.
 * Some of the characters have slightly different appearances. Pen, for example, has a more rounded hat, and the hole for his face is a semicircle instead of a circle, and he does not appear to have any missing teeth. Jake's jowls are bigger and his head is less rounded. The penguins are bigger, and blue instead of black. Princess Bubblegum's tiara has a red jewel on it instead of a blue one, and her hair is shorter. Ice King's beard is noticeably smaller and more pointy, and his skin tone is lighter. Lady Rainicorn's coloring is different, and her movements (in flying) are different. For example, her head waves with her tail follows the same movement unlike in other episodes her head is straight and her body waves.
 * At the start of the short, Jake is floating and seems to have the power to connect to the internet with his mind. However, that power is not seen in the Adventure Time series.
 * Ice King's drums are different in the animated short than in the series; his drums are black and they don't have the words "#1 BABE."
 * In Issue 3 of the Adventure Time comic, when Finn tells everyone how they can beat the Lich, he says that just like Abraham Lincoln said in the past and on Mars, you need to believe in yourself. That was a reference to when Pen (aka Finn) was frozen and he met Abraham Lincoln in the past and on Mars.
 * At the start, Pen's red sleeping bag was near the tree. But when he starts making booping sounds like a computer, it is gone until they start dancing.
 * In Issue 9 of the Adventure Time comic, Finn and Jake accidentally traveled back to the animated short, where Finn recalls that he had people call him "Pen" back then because he was so into pens. When he and Jake depart, Finn leaves behind a note telling Pen he should go by his real name, and the two inadvertently take along the sleeping bag (explaining why it vanishes for no reason).
 * Pen uses math-related phrases, such as "algebraic," (after LR flies over them) "mathematical," and "rhombus" (after riding the penguins).
 * The background and designs of the places are not as rummaged and littered as they actually are in the series.
 * This is the only time Earth is depicted without a chunk of it missing and the continents where they are supposed to be.
 * The scene where Jake was meditating looks similar to a scene where he meditates in the episode "Marceline's Closet".
 * When Pen and Jake elevated into Ice King's Castle, Jake's boots disappeared.