Flame Princess

Flame Princess is the princess of the Fire Kingdom as well as Finn's new love interest and current girlfriend. When Jake asks Flambo if he knows any princesses Finn's age, he responds that he knows "just the skirt... and she's way hot." Flame Princess is locked in a lantern in the main chamber of the Fire Palace when Jake first encounters her.

Finn
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 doesn't 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 from the bush to her aid. He then tells her that he was worried about her and thinks that she's beautiful. This causes her to glow, literally and figuratively, 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 his claims that he was not trying to hurt her were genuine.

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 the it and its citizens on fire. Finn and Jake attempt to stop her with robo suits, 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 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 doesn't 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's 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 two, which is kissing. Later in the episode, Finn goes on a date with Flame Princess (off-screen) and tells Jake that, he wasn't able to kiss her yet, so he is still on tier one. Jake advises Finn to write a poem for Flame Princess in order to move things along. Finn tries to think about Flame Princess' qualities to which he says, "...she's bright. She's beautiful. She makes me feel confused, like somethings filling up my chest—like I can't breathe. Is it because she's so dangerous?" Finn 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's 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's 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. Finn picks her up and tells that he needs her to be okay. He then breathes into her mouth, which causes her to re-ignite. Jake pulls them out of the hole and both of them are alright. Finn picks up a rock and kisses it, then hands it to Flame Princess who kisses it as well.

Jake
Jake 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; Though, she does not react much when Prince Finn kills Jake. Jake does not interact much with Flame Princess in the show, but in "Burning Low" Jake gives advice to Finn about how to progress their relationship, showing that Jake has approved of her.

Denizens of the Fire Kingdom
She seems to have little concern for her own subjects. In "Incendium" she transforms a small group of citizens into flambits solely because they were whispering.

Princess Bubblegum
There has not yet been any direct contact between Flame Princess and Princess Bubblegum in the series, but Princess Bubblegum revealed in "Burning Low" 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 and what "extreme romance" would do to it.

Appearance
Flame Princess has long orange-red hair that is made of fire and as such flows above her head. Her skin is yellow-orange and she wears a long, sleeveless dress that touches the ground. She doesn't wear shoes, though her dress usually hides her feet from view. She has two diamond-shaped, red gems; one on her forehead and the other on the front of her dress. She has black eyes that sparkle white and yellow in the light of her fire as shown in the screenshots on the right.

When her flames are doused, her skin changes to a pinkish-gray hue, and her hair falls down her back and becomes a dull shade of maroon. Once in dry conditions, she returns to her normal appearance quickly. When Flame Princess is deprived of oxygen she turns a light shade of blue, as seen in "Burning Low." Flame Princess has a body-type similar to Jungle Princess and Fionna's; she is curvier than most humanoid characters in Adventure Time.

Abilities
Being a Fire Elemental, Flame Princess is able to conjure up flames at will, transform other citizens of the Fire Kingdom into flambits, transform into a much larger, more dangerous form composed purely of fire, hurl fireballs that can vary in size, and separate her body into distinctly separate groups of flames (shown when she ambushes Finn in "Hot to the Touch"). She appears to be able to consciously extinguish fire she has created; she does this when she notices Finn crying. She can also float and move very quickly, both of which leave a trail of flames.

She has a weakness to water, shown after unintentionally setting off some of Princess Bubblegum's liquid pyrotechnics and when she puts her hand into a pond. The liquid pyrotechnics caused her to become unconscious, and touching the water in the pool caused her pain. The fires that Flame Princess makes are a part of her, and stomping on or dousing the fire hurts her.

She has an extremely unstable makeup. If her elemental matrix is exposed to extreme romance, she would burn through the Earth's crust and set off a series of reactions, causing a meltdown that would burn up the planet from the inside. This reaction was started when Finn kissed her in "Burning Low," but the crisis was averted.

Personality
Flame Princess has a volatile personality. She is described as "passionate" by Finn, "evil" by the Flame King, and "intense" by Pendleton Ward. The Flame King also remarks that she is difficult to control. She seems to be very sensitive and quick to judge. She is also prone to unprovoked fits of aggression, as shown when she throws fireballs at her citizens just for whispering. Flame Princess is also impressionable in a positive way. She is very happy when Finn calls her beautiful. She was also interested when Jake was giving her gifts in the episode "Incendium" and excited when her dad let her date "Prince Finn;" Though, this excitement quickly turns to anger when "Prince Finn" rejects her.

In the episode "Hot to the Touch," Flame Princess shows curiosity about her new surroundings by examining flowers. This sets them on fire and she seems a bit surprised by the reaction, indicating she doesn't know much about lands other than the Fire Kingdom. At the end of the same episode, she shows that she likes Finn, but thinks that they can't be together because they are opposite elementals (she thought Finn was a water elemental because of the tear that she felt from him).

In "Burning Low," she seems to be calmer and able to handle a part of her flame being doused. This is illustrated when Finn jumps into the water while his foot is on fire, but she doesn't react.

Major appearances

 * "Incendium"
 * "Hot to the Touch"
 * "Burning Low"

Minor appearances

 * "King Worm"

Quotes
See Flame Princess/Quotes

Trivia

 * Pendleton Ward and the show's cast first introduced Flame Princess at Comic-Con 2011.
 * Natasha Allegri has drawn Flame Prince, a gender-swapped version of Flame Princess, in her artwork, but he has yet to appear on the show.
 * Flame Princess is the only known princess to have invaded another kingdom by herself.
 * In the original storyboard for "Hot to the Touch," Flame Princess was supposed to kiss Finn; however, the idea was dropped.
 * When Flame Princess transforms into her larger form, her face resembles that of her father, the Flame King.
 * Flame Princess's appearance in King Worm is her first appearance in an episode without a fire-related title, this also marks Flame Princess's first minor appearance.
 * As of "Burning Low," Flame Princess and Finn are dating.
 * When Finn and Flame Princess kissed they had an open mouth kiss; when Finn kissed Princess Bubblegum in the past they only had closed mouth kisses. This is the first open mouth kiss.