28 Episodes · Premiered December 7, 2008 · Ended September 27, 2010
The season follows the adventures of Finn, a human boy, and his best friend Jake, a dog with magical powers to change shape and grow and shrink at will. Finn and Jake live in the post-apocalyptic Land of Ooo. Along the way, they interact with the other main characters of the show: Princess Bubblegum, The Ice King, Marceline the Vampire Queen, Lumpy Space Princess, and BMO.
Princess Bubblegum is captured by the Ice King, and it's now up to Pen (later renamed Finn) and Jake to save her!
Finn and Jake must team up with the Ice King to stop a misbehaving wand.
Princess Bumblegum's latest experiment accidentally unleashes an undead horde upon the Candy Kingdom.
Jake is bitten by Lumpy Space Princess and begins to transform into a Lumpy being. In order to find a cure, Finn is travels to Lumpy Space.
After the Ice King kidnaps a large group of princesses, its up to Finn and Jake to free them.
Tree Trunks joins Finn and Jake on an quest, but finds her talents for adventuring leave something to be desired.
Finn and Jake go on a quest for the titular magical book that would prove them worthy of being righteous heroes. After passing through a series of trials and tribulations, Finn acquires the legendary book.
A strange creature attracted by Finn's auto-tuned singing voice follows the duo to their home and they keep him as a pet. Soon, however, the creature begins to show signs of sickness, and Finn and Jake realize the creature needs the love and attention of its mother. They then return it to its nest.
Finn believes that Princess Bubblegum's new friend, a literal heart named Ricardio is evil and is proven right after learning that Ricardio is the heart of the Ice King. Ricardio reveals that he wants to "make out" with Bubblegum's heart, but he is defeated by Finn and Jake.
Finn and Jake fall victim to their own laziness when they delegate their adventuring responsibilities to a group of businessmen they thawed from an iceberg. Eventually, the businessmen's efficiency causes them to become hazards to others, and they are refrozen into an iceberg.
Jake feels overwhelmed at not having enough time for Finn and his girlfriend, Lady Rainicorn, so he tries to get them to hang out more. Eventually, Finn and Lady Raincorn become closer than Jake is comfortable with, and he starts feeling jealous.
Finn, motivated by an upsetting experience when he was a baby, tries to reconfirm his desire for helping people out when confronted with one problem after another stemming from a violence-hating mountain.
Finn and Jake are coaxed by a skeleton man to enroll in a course for free magic powers. After becoming full-fledged wizards, they realize they were tricked into helping stop an asteroid for all of eternity. Finn rejects the status quo and thinks of a different way to avert the crisis.
Finn and Jake search the land of Ooo for a new home after a vampire queen named Marceline claims the duo's treehouse as her own. Eventually, Marceline relents, because she thinks Finn and Jake are "cool".
Finn and Jake, in hopes of helping a little girl named Penny get back her stolen basket, enter into a city where everyone is a thief, and become slowly corrupted by their surroundings.
After Jake steals one of the Witch's donuts, she steals Jake's powers and won't give them back unless he apologizes to her. During a series of events trying to find a way to get Jake's powers back, Finn's life is then held on the line, but will Jake's new laziness get the best of him?
Finn creates a Never-Ending Pie-Throwing Robot (Neptr) to prank Jake, but it unexpectedly comes to life! Yet when he decides to use some of the Ice King's power to further develop it, this ultimately leads to a moral dilemma for the new living machine.
Finn discovers he's afraid of the ocean, so he enlists Jake's help to overcome his fear or risk failure.
The Ice King is finally getting married, but consults Finn and Jake on whether or not to go through with getting hitched or keeping his life of abducting princesses.
Finn descends into a dungeon in hopes of finding adventure, but ultimately finding various obstacles that better fit being handled by Jake than himself alone.
During a mishap accidentally caused by Finn,Princess Bubblegum becomes green and bald, and blames the Duke of Nuts for it, thus making Finn think he's a bad guy. Finn and Jake have no choice but to find the Duke of Nuts on Bubblegum's order.
After a magic man turns Finn into a giant foot, he and Jake team up with a band of similar body part freaks to set things right and try to turn themselves back to normal.
When Finn and Jake see a bullying ogre named Donny, they help him turn his life around, unaware of the ecological consequences of their action.
Finn takes the place of Marceline's henchman, and he finds out how hard it is to obey her strange ways.
When a knife storm forces Finn and Jake to stay inside, they discover the out-of-control power of Jake's imagination.
Finn and Jake capture Ice King under order of Princess Bubblegum without even knowing what he has done wrong.
Finn and Jake discover Billy, the greatest hero who ever lived, and try to help other people without using violence in their methods.
When the gold owned by several beings were devoured by a creature called the "Gut Grinder," Finn and Jake set out to discover who the culprit is, while trying to sustain Jake's thoughts that he is the actual Gut Grinder.
