Being a hero, Finn has become quite popular in the Land of Ooo, starting many friendly relationships.
Jake EditAs housemates, brothers and best friends, Finn and Jake share a very deep and strong bond. Having been raised together by Jake's parents, the duo share a relationship similar to that of siblings, with Jake acting as Finn's older brother. Though they have an unconditional love for each other, Finn can get frustrated with Jake because of his laziness and lack of motivation, shown especially in "The Witch's Garden." As a more laid-back character, Jake often tries to relax Finn's fiery personality in the face of a struggle, advising him not to worry in most situations. Though he sometimes leads Finn down the wrong path, Jake genuinely means well for his companion and is usually an encouraging and protecting figure in Finn's life. Finn and Jake have saved each other's lives on several different occasions, and often adventure throughout the Land of Ooo together.
A unique part of Finn's relationship with Jake, is that Jake is able to tell when Finn is about to cry, as shown in the epsiode "Freak City" and is stating to be a "mother daughter thing".
Lady RainicornEditFinn became friends with Lady Rainicorn after Jake wanted to hang out with both of them at once in the episode "My Two Favorite People." At first Jake regretted introducing the two, but in the end he was glad it happened. Finn and Lady Rainicorn still share a close bond, despite the fact that Finn can't understand Lady Rainicorn's fluent Korean.
Princess BubblegumEditFinn and Princess Bubblegum kissing.Finn had a rather obvious crush, which he denied before the events of the episode "Wizard Battle," on Princess Bubblegum, whom he occasionally calls "Peebles" and other nicknames out of affection. He is known to interact with her more than any of the numerous other princesses of Ooo, and would jump at the chance to do anything for her. Finn becomes very protective and jealous when someone else comes between them, as seen in "Ricardio the Heart Guy," in which he sought to one-up Ricardio (obnoxiously performing the Science Dance, as a desperate ploy to attract Princess Bubblegum's attention) and expose him as a villain. Though the princess is seemingly oblivious to Finn's affection, she often calls on him for any royal need. In "The Real You," Princess Bubblegum kisses Finn on the cheek, and he faints a moment after the kiss.
Finn eagerly hoped to win the princess over with his heroic deeds. Finn and Princess Bubblegum share a staunch sense of morality and often work together to bring justice and balance to the Land of Ooo. Taking several dangerous and tomboyish cues from Marceline in "Go With Me," Finn tries to set up a movie date with Princess Bubblegum, who banishes Finn from the Candy Kingdom until he stops "acting like a psycho."
In "Mortal Folly," when Finn and Jake are chasing the Lich King, the Ice King persistently nags them to give him their blessing to marry Princess Bubblegum. When the Ice King says, "It's not like you want to marry her," Finn blushes and angrily throws a rock at him. Earlier in the episode, before embarking on their pursuit of the Lich, Princess Bubblegum gives Finn a pink, heart sweater that she knitted for him. This sweater would later protect Finn against the Lich using the "power of liking someone a lot," as Finn put it. (He later refers to the sweater as his "like-like sweater.")
In "Mortal Recoil," Finn outwardly confesses to the princess that he "likes her a lot," although it is unknown whether she actually heard him, as she was still possessed by the Lich at the time. Princess Bubblegum, whose incomplete reconstruction at the end of season two (resulting from the candy surgeons' inability to completely recover all the pieces of her bubblegum body) caused her to revert to her 13-year-old self, hugs Finn after her recovery and calls him "hero." They later share a kiss in "Too Young." However, his grip on the princess' heart loosens after her re-aging and she can only remember the hug (though she was joking, as confirmed by Natasha Allegri). Finn feels beaten afterwards, but a pep-talk from Jake brought his spirits back up. In "Wizard Battle," Finn got a kiss from Princess Bubblegum again after winning the Wizard Battle where she kisses him and then slaps him for cheating.
As of "What Was Missing," it is revealed that Finn has kept Princess Bubblegum's wad of hair from "To Cut a Woman's Hair" and spends quite a bit of alone time with it, as stated by Jake.
After being rejected several times, in "Incendium," Finn becomes deeply depressed and cries over Bubblegum by a little shrine he constructed made up of two framed pictures of her, his lock of her hair, and a pool of his tears. He becomes enraged and states that he'll kill whoever started a fire that burned his two pictures of Bubblegum. After his brief encounter with the Flame Princess (who started the fire) and saying that he likes her, and later saying that he thinks he has a crush, it is unknown if Finn has completely moved on from Princess Bubblegum or if he had just been distracted by the commotion and a new princess his own age, exhausted his tear supply, and/or only somewhat moved on due to his new crush.
In "In Your Footsteps," Jake says that Princess Bubblegum was his ex-girlfriend, but Finn replies they "never went steady."
In "Burning Low," he thinks the Princess Bubblegum is jealous after hearing from Jake. When he goes to write poetry for Flame Princess, Bubblegum finds him, saying, "I'm glad you understand why you can't be with Flame Princess." This makes him angry, and he reveals to her that he was formerly in love with her, but because she didn't love him back he is ready to move on. Bubblegum also knows that if Finn and Flame Princess kiss she would destroy the world from the inside out.
In "The Lich," Finn shows animosity toward the Princess when she accidentally cuts him with her scissors while he is stealing the jewel from her crown. This is possibly due to his being influenced by the Lich impersonating Billy.
In All the Little People, Finn puts himself and Flame Princess together before putting himself and PB together.
MarcelineEditThough he initially considers her an enemy in her debut, "Evicted!," Finn quickly befriends Marceline the Vampire Queen, as he learns that her seemingly evil ways are just playful teasing. A rowdy and adventurous character, Marceline and Finn share the same vigor and thirst for danger. One of the key reasons why they managed to forge a friendship is that Finn saved her life in "Henchman" when Jake exposed her to direct sunlight and threw garlic at her in a misguided attempt to save his friend Finn. In the same episode, Finn, in an attempt to convince Jake of her generally wholesome ways, calls Marceline "a radical dame who likes playing games." As previously stated, Marceline loves to mess with Finn's head. Despite Jake's fear of Marceline (and of all vampires), Finn enjoys spending time with her so that they can be "awesome together." In "Go With Me," Finn asks her to go to "Couples-Only Movie Night," but only as a friend. Being (mutually) disgusted to the point of vomiting by the idea of kissing (although ironically she has kissed him on the cheek at least twice), Marceline has no interest in dating Finn. In "Marceline's Closet," he accidentally sees her naked when Jake tells him to see if the coast is clear for them to get out of her house, causing him much discomfort.
Ice KingEditAs the story's recurring antagonist, Ice King and Finn are frequently at odds. Finn is prone to impatience and quick aggression around him but can show him sympathy, as in "When Wedding Bells Thaw." However, Finn's aggression never outweighs his compassion, honor, and respect for life, as evidenced when he refused the opportunity to slay Ice King as Billy had slain the Fire Count. Similarly in "Mortal Recoil," Finn, albeit grudgingly, trusted and united with Ice King against their common enemy of the Lich-possessed Princess Bubblegum. Further contributing to their differences, Ice King competes with Finn for Princess Bubblegum, until the closing scene of season two. This mutual attraction for Princess Bubblegum can be clearly seen in "Mortal Folly," where Ice King continually pesters Finn for consent to wed Princess Bubblegum. Upon Ice King's saying, "It's not like you wanna marry her," Finn blushes and hurls a rock at Ice King.
Although Finn and the Ice King started out as bitter rivals, their relationship progressed to a friendly rivalry, then an odd friendship in its own right, and finally a genuine friendship.
The Ice King does not really hate Finn and Jake, as he only fights with them because they are opposing each other in terms of morals. He frequently tries to be friends with them (in his own, misguided way) and has willingly made alliances with them. In the episode "Still" The Ice king freezes Finn and Jake so they can have "bonding time." It was shown in "Hitman" that while Finn and the Ice King are rivals, they are not enemies, and don't harbor any real malice towards each other. The Ice King made it clear that he doesn't want to kill Finn- the most he would do is punch him in the belly and make him vomit up his lunch. At worst, they are battling rivals, as Finn openly disapproves of the Ice King's habit of stealing princesses and causing mischief. At best, they are playful rivals, even friends. In "Holly Jolly Secrets Part II," the Ice King has a locket with the pictures of Finn and Jake. Near the end of the episode, the two are shown snuggled up side-by-side by a roaring fire, wearing ugly Christmas sweaters. Finn's attitude towards the Ice King has softened since discovering the tragic secret of his origin, and his compassion for people in distress outweighed his petty squalls with him enough to be his friend.
BMO lives with Finn and Jake in the Tree Fort. He serves as their living video game system, film editor, camera, and many more portable electric items. He appeared in the eighth episode ofAdventure Time, so it is obvious he has been with them for a long time. In "Video Makers," BMO records the footage requested by Finn and Jake, although they disagree on what genre of movie it will be, so they leave him a note that tells him to keep only the best footage and present it at the Movie Club. He ends up bringing them together by using both the action and comedy/romance footage and singing his BFF Song, so it appears he doesn't take sides with either of them. In "Incendium," BMO's video game music inspires Finn to sing All Gummed Up Inside, then BMO helps watch him while Jake courts Flame Princess, and also pulls a kancho prank on him.
Finn first meets Flame Princess at the end of the episode "Incendium." During the episode, Jake had been posing as Finn trying to court her because he believed that Finn, depressed after being rejected again by Princess Bubblegum, needed a new love interest. However, when Flame Princess's father tells Jake that she is evil, Jake tells her (disguised as Finn) that he doesn't like her, which causes her to become confused and angry and attack him, following him back to the tree fort where the real Finn is. She starts a fire in the house which burns the pictures in Finn's shrine to Princess Bubblegum, and he becomes enraged and runs to see who ruined his shrine. He is surprised to see it's Flame Princess. When she accidentally lights the liquid pyrotechnics left behind by Princess Bubblegum and douses her fire, he saves her and brings her into the house. When she regains consciousness, Flame Princess yells at him, "You! What's wrong with me huh?! You don´t like me?!" and Finn states, "I like you!" Flame Princess blushes. She then slaps Finn and warns him never to mess with her again, and flees the tree house. After she slaps him, he immediately wanted to know who she was. He then told Jake, "Dude, I think I have a crush." showing that he may be in love with her.In the continuation episode, "Hot to the Touch," she officially becomes Finn's new love interest. He asks Jake to help him find her, saying that he "peeped beyond her burning gaze" and that "she ain't evil," and the two run out to look for her. They spied her by a pond and hid behind the bushes to watch her. Finn affectionately likened her to "the steam off a puppy's nose searching for ham in snow" and "a cute little flower." When she curiously dips her hand in the pool and jumps back in pain, Finn rushes to her aid, surprising her. Finn admits to Flame Princess that he really likes her and they should be together, which causes her to glow brighter and makes small fires appear around her. Finn was surprised with the fire getting near him, so he tried to put them out, not knowing that by putting out the flames he was hurting Flame Princess. Angry and confused, she ran again and the brothers chased after her, then she ambushed them. However, the attack does not last long, and Finn confuses Flame Princess by trying to compliment her while she is trying to kill them. He then tries to explain his feelings again which causes her to blush, but she resists. Upset that when Finn makes her glow brighter, he puts it, she warns him that he "should not toy the emotions of a fire elemental." Flame Princess says that fire's purpose is to burn and proclaimed that this land (Goblin Kingdom) will be her own Fire Kingdom. Finn tried to convince her not to do it.
She refused and cast a wall of fire to back down Finn and Jake. When they flew to Goblin Kingdom with proof suits, Flame Princess attacked them with fireballs but they had no effect. She again shoots another fireball at Finn, but this was deflected and instead hit a cart. Jake extinguished the cart's flames, consequently hurting Flame Princess once more. Finn distresses that he doesn't want to hurt Flame Princess, but his morals say he must help the citizens of the Goblin Kingdom. Neptr, thinking he's helping, engages the foam blaster to extinguish her. However, Finn manages to stop Neptr from directly hitting Flame Princess and instead he hits Jake and a few of Flame Princess' flames, hurting again Flame Princess. Flame Princess then gets extremely angry and proclaims, "That is the last time you hurt me," and grows into her beast form, a towering human-shaped fire. A fiery tear from Flame Princess' right eye is revealed that she was harmed both physically and emotionally. Finn shouts, "No more! No more!" and literally rips himself out of his own suit and stands on top of it, shouting out to Flame Princess. However, he is ignored.Finn, angry and upset that he can't "just like a girl," begins to cry. A tear of his falls on the flames of Flame Princess, stinging her and catching her attention. Flame Princess watches Finn cry, confused and amazed, then stops her flames and approaches him. She says that now she believes that Finn is a Water Elemental because he "creates water," or cries. Flame Princess says that no matter how much they like each other, they can't be together because they are of conflicting elements. Finn tries to explain that he isn't, but Flame Princess has trouble understanding the concept and says even if they liked each other, they would only hurt each other. Finn replies, "No, I can take it. I mean...we can try." Flame Princess glows, touched that he "would defy nature for" her. She hugs him, and although he smiles for the first few seconds, Finn begins to burn up and pushes her away. Flame Princess then bids him goodbye. In "Burning Low," she and Finn are dating. She even thanks him for building her house and they hug each other. He decides to go to "tier two (smooching)" after another date, but only receives five hugs, which according to Jake, does not count as "tier two." Embarrassed, Jake then gives Finn the idea to write her a "sappy poem." Finn also gets angry at Princess Bubblegum for wanting him to stop seeing her. Then, when Jake is convinced what would happen if Finn kisses Flame Princess, he and Princess Bubblegum try to stop it, but arrive to see them already kissing. When Flame Princess falls into the earth's crust due to her instability, Finn goes in to save her, with Jake cutting off her oxygen supply. After using artificial respiration to revive her, they continue to date.
In "Ignition Point," Finn and Jake go to the Fire Kingdom to retrieve scented candles. In "Reign of Gunters," Finn takes the advice of a dating book called Mind Games and tries to act more mysterious, claiming he needs to keep all the ladies in a state of confusion; that way, he has "options in case Flame Princess doesn't work out."
In "All the Little People", when Finn put the little Flame Princess and little Finn together, little Finn approached her, and they smiled at one another. They divided a cookie and began eating it together.
The broke up in the episode "Frost & Fire," but later agreed to be just friends with each other after Flame Princess became Flame Queen, in the episode "Earth & Water". But they would become a couple again in a later episode.
When Finn traveled to Gene's mansion, he assumed Finn was just another greedy human. However, Finn came to ask Gene to free Jake, who had been imprisoned in an indestructible cage, Gene was touched. He gets along well with Finn and enjoys having fun with the human. It is quite obvious that Gene has a lot of respect for Finn and has gone out of the way to protect him on a few occasions. Out of boredom, Gene will occasionally create a new fanciful game such as "Gravity-Less Hockey" or "Space Ball" in order to pass the time with Finn and Jake.
After Gene's house is blown up "By a Goblintrollninjaghostthing", he takes up residence in the Tree Fort's laundry room, presumably due to his enjoyment of Finn's company.
Finn and Elf Prince seem to get quite along. He could been a friend of Finn already, since he was invited. It first was assumed they had some rivalry with Finn, since when Finn left he stuck his tongue out. But in later episodes this was strengthened because Elf Prince begun a relationship with Princess Bubblegum, although they later broke up again. After those events Finn and EP became better friends and even went on adventures together.