Adventure Time with Finn and Jake: The Journey is a series when Finn, Jake and their friends go on a perilous adventure to defeat King Demonicon.
Finn, Jake and their friends go on a adventure.
- Finn Mertins: Finn is a 14-year-old human boy who loves nothing more than going on adventures and saving the day. He wears a hat that covers his extremely long flowing golden hair (which he cuts off and is seen to progressively grow back in following episodes). He is prone to exclamations and outbursts including "Mathematical!" and "Algebraic!". When Finn was a baby, he did a 'boom boom' leading to his adoption by Jake's parents: Joshua and Margeret. Considering himself a hero, Finn has a lust for adventure and swore long ago that he would help anyone in need, but being so full of energy, he has trouble in situations that require him to do tasks other than fighting monsters. He has some fears, such as the ocean, clowns, spiders, and being judged by older people due to his age.
- Jake: Jake is Finn's best friend and adoptive brother. He is a 28-year-old (in "magical dog years") shape-shifting dog. His magic powers allow him to stretch or shrink any part of his body to any shape and almost any size, ranging from becoming gigantic to becoming incredibly small. Acting as a confidant and mentor to his energetic brother (though he has a tendency to give somewhat sketchy advice), Jake has a laid-back attitude in most situations, but loves adventure and will eagerly fight when he needs to. In the episode, "The Apple Thief", it is revealed that Jake used to steal bikes and purses from old ladies. His powers help Finn considerably in combat and transportation, but are also sometimes used as nothing more than jovial forms of expression. Jake is in a relationship with Lady Rainicorn, who is pregnant with their children. He is quite skilled at playing the viola, which houses a worm called Shelby.
- Princess Bubblegum – Princess Bubblegum is a bubblegum humanoid, comparable to the inhabitants of Candy Kingdom, which she rules, who are all composed of types of desserts and candies. Her proficiency in science and fluency in Korean and German are a testament to her high intelligence. While Princess Bubblegum is typically kind and well-mannered, her temper can be a powerful force when provoked. Marceline reveals that Bubblegum's first name is "Bonnibel".
- Lady Rainicorn – Lady Rainicorn is a half-rainbow, half-unicorn creature and Jake's girlfriend. She can turn objects and people different colors. Her origins can be traced back in which Jake explains how rainicorns and dogs have been battling over the Crystal Dimension for centuries. Rainicorns having a taste for human flesh, when her parents attempt to eat Finn. However, Lady herself has never shown hostility toward Finn and always has a kind disposition with him. She can fly because her body intercepts light and can dance on it, which also explains her movement and why she has a rainbow pattern. Jake describes her as "the Rowdy Queen" because she can have fun and fight evil. Despite being unable to speak the major language depending on the dubbed versions, she is able to understand it. As the TV series goes on, Jake and Lady's relation continue to grow, and in the end, it is revealed that Lady is pregnant.
- The Ice King – The Ice King is the main antagonist and sometimes a protagonist of the series who is around 1,000 years old. The Ice King frequently steals princesses throughout Ooo to forcefully marry them, Princess Bubblegum and Marceline being his usual targets. His magic abilities to freeze things by hurling frozen lightning bolts, summoning snow monsters, and flying with his beard come from the magical crown he wears. He is a master of the martial art of Frijitsu, a technique calling upon the power of ice. Though defined as a spociopath by many, the Ice King is actually lonely and misunderstood, having a generally benevolent relationship with the penguins (primarily one named Gunter), along with the snow and ice beasts who populate his realm, and secretly envious of Finn and Jake for being such good friends. Ice King's origins are revealed when one of his home-video movies showed that he was originally a human antiquarian named Simon Petrikov who was taping a documentary of a crown he bought from an old dock worker in northern Scandivavia, predating the Mushroom War. Wearing the crown, Petrikov begins to lose both his mind and then his fiancée Betty, the source of his subconscious need for princesses, deteriorating in both mind and body over the years into his current state. The Ice King has a photograph from before the Mushroom War of himself (as Simon) in posession of the Enchiridion.
- Lumpy Space Princess – Lumpy Space Princess (or "LSP" for short) is the princess of Lumpy Space, an alternate dimension. Like all her people, LSP is an extraterrestrial creature known as a "Lumper" which looks like a floating purple cloud with arms and a face, and can convert other beings into Lumpers by biting them. LSP is spoiled and sarcastic, constantly seeking to improve her appearance from getting cosmetic surgery to punching herself into a ball in order to be less lumpy. In later seasons, she is shown as being proud of her "lumps" and makes it known on more than one occasion that her lumps are the source of her attractiveness. She is often shown living outdoors with salvaged furniture and appears to be homeless, because she has either run away from home, or is seeking independence from her parents. She speaks with a thick (albeit masculine) Valley Girl Accent. Her parents are the king and queen of Lumpy Space. It appears that LSP can only float above the ground and cannot fly, although she can turn this off by touching the star on her forehead.
- The Beginning of an Adventure: Finn and Jake start their quest with their friends.
- Ice King's Trap: Jake gets trapped by Ice King.