Her father, the Flame King, understands his own daughter as "evil," having said so during "Incendium" even in introducing her to "Finn" (Jake molding part of his body into a Finn-shape) when they first meet. In "Ignition Point" Flame Princess admits to hating that her father locked her away in the lantern for all these years and thus refuses to go back to Fire Kingdom after she finally leaves it behind when meeting Finn.
However, Flame King's concept of his daughter being evil is merely a factor of all Fire Kingdom citizens being evil and traitorous to one another, with him believing her like others yet with physical instability that would cause harm to anyone around her. He slightly could believe his daughter could gain a "good" alignment if she hung around people like Finn, but he does not know if it could work due to Flame Princess' fiery nature.
He later attempts to send subliminal messages to her while she sleeps by saying "evil," but it quickly stops when Flame Princess wakes up and sees this, leaving her shocked. He does so again at the start of "Vault of Bones" but stops upon realizing that she is not alone, causing Finn to look for a way to counteract his influence.
In "Earth & Water," when Flame Princess was born, Flame King feared she would become so powerful that she would overthrow him. So he had one of his servants to take her to the woods for her to perish. However, the servant took pity on her and gave her to a woodsman, but she wandered around and proceeded to burn the woodsman house and the surrounding forest. She was found by Princess Bubblegum, who brought her back to her father, where the Princess demanded he control his daughter. So, he locked her in a oil lamp-like cage. When Flame Princess discovered this, she and Cinnamon Bun went to the Fire Kingdom, overthrew her father, and locked him in the same cage she was once in.
Flame Princess has two unnamed younger brothers and one unnamed older brother serving in the military.
Flame Princess has two cousins, Furnius and Torcho, who hate her father because he killed their father in order to take over the Fire Kingdom.
She also has an aunt and uncle who are very judgmental.
JakeEditJake enters the Fire Kingdom to court Flame Princess on behalf of Finn, who is feeling heartbroken after having been pushed away by his previous love interest, Princess Bubblegum.
Jake sings her a song and accidentally kills her father's jester by spilling water on him, both of which she apparently enjoyed; however, she does not react much when "Prince Finn" kills Jake.
In "Burning Low," Jake does not interact much with Flame Princess but they seem to be friends and Jake has approved of her; he even helps Finn in courting her with a poem.
In "Ignition Point," they interact much more and they seem to be comfortable with each other; it was Jake who suggested going to the Fire Kingdom to get her the scented candles.
Jake seems glad to see Finn happy with Flame Princess, as he was the one to seek her after Finn was rejected by Princess Bubblegum. Jake also keeps his distance when Finn and Flame Princess are together, as shown in "Burning Low" when Finn asks Jake if he wants to check out Flame Princess' new house and he politely refuses and tells them to go ahead. Also in "Vault of Bones," while Flame Princess and Finn are playing cards, Jake offers them chamomile tea to show his support of their relationship.
In "Jake Suit," Jake embarrassed Finn in front of Flame Princess and her less-evil family members by making him semi-naked and singing the Baby Finn Song as he thought that would make him win. However, he was unsuccessful because Flame Princess spotted him inside Finn's mouth while talking to him (Finn). She thinks that it was pretty hardcore of Jake for doing that to Finn.
In "Earth & Water," when Flame Princess submitted herself to experiments by Princess Bubblegum to control her emotions, Princess Bubblegum had to leave to help Finn and Jake so she had no choice but to put Cinnamon Bun in charge of the experiment. However, he brought Flame Princess to his house to talk. Liking his honesty and after recalling that it was Princess Bubblegum who had her father put her in the cage where she spent her childhood, they both went to the Fire Kingdom and overthrew the Flame King and enacted a policy where lies were not allowed.
Lumpy Space PrincessEdit
In the episode "Fire Friend" Flame Princess became best friends with Lumpy Space Princess.
Flame Princess does not actually meet Finn in person until the very end of "Incendium." After she is doused with liquid pyrotechnics, she unconsciously falls off the roof of the Tree Fort. Finn catches her as she is falling and brings her inside. She regains consciousness and angrily asks Finn why he does not like her; Finn replies that he does like her, which causes her to blush in surprise. Confused by Finn's apparent fickleness, she slaps him and warns him never to mess with her again—unaware that Jake was the original "Prince Finn."
In "Hot to the Touch," Finn wanders into the woods to search for the Princess, after asking Jake about her and saying he really likes her. When Finn finds Flame Princess he watches her from a bush at first, calling her innocent like "the steam off a puppy's nose searching for ham in the snow" and "a cute little flower." She touches a pool of water, hurting herself, and Finn jumps out from the bush to her aid. He then tells her that he was worried about her and thinks that she is beautiful. This causes her to glow, causing some fire to spread around Finn and herself. Finn puts out the fires in a panic which causes her pain, causing Flame Princess to believe that Finn is intentionally hurting her. She leaves in a huff without allowing Finn a chance to explain, not listening to his claims that he was not trying to hurt her.
After a brief chase, she concludes Finn is trying to impede her, so she decides to turn the Grass Lands into her own fire kingdom. She begins by heading for Goblin Kingdom to set it and its citizens on fire. Finn and Jake attempt to stop her with Robo suits made by Neptr, but Finn only attempts to talk her out of it rather than put out her fires. When Finn realizes he cannot make her understand his feelings, he tears a hole in his robo suit and cries wishing he could "just like a girl." One of his tears falls onto the flames as she is walking away from him, causing her to turn around and witness him crying. She becomes convinced that he is a "Water Elemental," saying that all he does is cry and cry all the time. She comes to the conclusion that they are opposite elementals and that even if they like each other, they would hurt each other. However, Finn suggests that they try to make it work and that he can take it. She seems happy that he would want to defy nature for her, and both lean in to hug one another. As they hug, Finn gets burned and pushes her away. She looks at him appearing unsure, and then leaves saying, "Bye, Finn."
In "Burning Low," she and Finn are dating. Finn helps her build a new house in the Grass Lands out of wood scraps, and she tells him that she loves it. Her flames trail over to Finn's foot and he is surprised to realize that it does not hurt as bad as it used to; though, once the flames crawl up his leg he screams in pain and jumps into the water. Once he is out of the water, Finn and Flame Princess hug; although, Finn has to wear many layers of tinfoil to protect himself. While walking home, Finn asks Jake for advice about dating, to which Jake explains the concept of "tiers" and tells Finn that he should move on to Tier 2, which is kissing. Later in the episode, Finn goes on a date with Flame Princess off-screen and tells Jake that he was not able to kiss her yet (though he got 5 hugs), so he is still on Tier 1. Jake advises Finn to write a poem for Flame Princess in order to move things along. Finn tries to think about Flame Princess' qualities, and he ends up going outside and watching the sunrise, which gives him inspiration to write. He takes the finished poem over to Flame Princess' new house and reads it to her. After he is done they stare into each other's eyes and kiss. The kiss triggers a reaction and causes her to burn so hot that she melts through the ground. As she is falling, Finn grabs Jake's arm, ties it around himself and jumps down after her. Flame Princess' reaction is halted by lack of oxygen, and when Finn catches up to her she is extinguished and passed out. Though nearly out of oxygen himself, Finn picks her up and tells that he needs her to be okay. He then gives her, which causes her to re-ignite (though Finn passes out from lack of oxygen). Jake pulls them out of the hole and both of them are all right (parts of Finn's face are burned from the kiss). Finn picks up a rock and kisses it, then hands it to Flame Princess who kisses it as well.
In "King Worm," Flame Princess is feeding Finn (whom she calls "honey") soup; first lovingly, then angrily when he hesitates (he was confused, having been with Princess Bubblegum as her king and husband seconds earlier). However, Finn soon discovers that he is in a dream and she is not the real Flame Princess.
In "Ignition Point," Finn and Jake travel to the Fire Kingdom to retrieve Flame Princess' scented candles. While there, Finn finds out that Flame Princess is evil, but he seems pleased to know that she could possibly be turned to good.
In "Reign of Gunters," Finn takes the advice of a dating book called Mind Games and tries to act more mysterious.
In "Vault of Bones," she went to the Vault of Bones with Finn to prove to herself that she is good. He teaches her properly how to dungeon crawl, but she thought that his methods were boring (due to her impatient and destructive personality) and told him that she was not having fun. After Finn allows her to do things her own way, she proceeds to burn everything down with her elemental powers. When a Giant Goo Skull captures Finn, she rescues him by intimidating it and calls him her boyfriend for the first time. At first, Finn thought he was going to be burned alive because of how Flame Princess approached the Goo Skull, but after he is rescued, Flame Princess says she would never hurt her boyfriend. At the end of the episode, Flame Princess thanked Finn for taking her to the dungeon and suggested that they should go to other dungeons sometimes.
In "Jake Suit," she invited Finn at her house to meet her less-evil family members. She totally did not even mind that he made a fool of himself once she found out it was because of a bet with Jake. She believes that Finn will win and cheers him on, giving him the support he needs to survive the final stretch of Jake's gauntlet.
In "Frost & Fire," Finn and Flame Princess were interrupted by Ice King in the middle of a picnic. After Flame Princess beats up Ice King for insulting her, Finn started to have weird dreams with the Cosmic Owl in it, but kept waking up before he could finish the dream. Finn tries to get Flame Princess and Ice King fight by writing insulting messages about them and claiming the other sent it. This, however, leads to Finn attempting to apologize and to continue their relationship, but to no avail as Flame Princess leaves saying "...I need some time alone."
In "Too Old," it is revealed Finn took Flame Princess's words the wrong way, and thought she had dumped him, and therefore made one last attempt at Princess Bubblegum. It failed as usual, and he told Jake he has to "Patch things up with Flame Princess." So it is unknown if they got back together or not, as Jake ominously stated Flame Princess could have already replaced Finn with a new boyfriend.
In "Earth & Water," Flame Princess had troubles controlling her emotions again after her breakup with Finn and was confused if she wanted to be with him again. She later befriends Cinnamon Bun when Princess Bubblegum leaves her unattended in the middle of a test and tells him that sometimes friends are "hard to understand" and that they were "just playing mind games." This may be due to Finn keeping all the ladies in confusion after reading the book about Mind Games in "Reign of Gunters." Later in the episode, Flame Princess overthrew Flame King and became the new ruler. When Finn tried to apologize to her, she accepted his apology. He asked her if they were still going out, she said no but they could still be friends and that he can come by anytime as long as he is completely honest with her. Finn and Flame Princess reestablished their friendship in "Bun Bun".
Princess Bubblegum revealed to Jake in "Burning Low" that Flame Princess is unaware that she was the one who had the Flame King lock up his daughter in the lantern due to her physical instability. Princess Bubblegum knows, in great detail, about Flame Princess's elemental matrix, what "extreme romance" would do to it, and how to stop the resulting reaction. In "Earth & Water," Flame Princess agrees with Princess Bubblegum to help her by creating a scientific model that described her complete elemental matrix, so she could isolate and suppress her violent feelings. She claims that she does not know if Princess Bubblegum is her friend when Cinnamon Bun asks her. After Cinnamon Bun asks Flame Princess why Princess Bubblegum put her into "baby jail," saying that this was "a weird friend thing," she finally realizes that it was Princess Bubblegum's idea to lock her in a lantern while she was a baby. It is unknown if she holds any actual bitterness towards Princess Bubblegum for this.
Before there had been any direct contact between Flame Princess and the Ice King it seemed that he knew her because he mentioned Flame Princess in "I Remember You," probably from hearing about her from Finn and Jake. Flame Princess is one of the princesses that the Ice King calls "okay."
In "Frost & Fire," after the Ice King called her a weirdo for hugging a log, she punches him in the stomach and started a fight. She slaps him in the face and sets his underwear on fire before kicking him back to Ice Kingdom. Later in the episode, Finn forged an insulting letter to make Flame Princess and Ice King fight again in order to complete his dream. The fight escalates into a huge explosion, causing Flame Princess to turn into a giant form. Ice King retaliates by controlling his Ice Mountain, like a giant warrior. He blocks her attacks and gets her into a headlock. However, she grows bigger and defeated him by toppling down his warrior. Flame Princess continues to destroy the Ice Kingdom until she found out that Finn was the one who wrote the letter.