Flame Princess

Flame Princess is the princess of the Fire Kingdom and 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, so she merely spectates during most of Jake's visit.

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 quickly regains consciousness and angrily asks Finn why he doesn't like her, to which Finn replies that he does like her causing her to blush in surprise. Confused about how Finn could say one thing and then immediately contradict himself, she slaps him and warns him never to mess with her again - she was unaware that it was Jake as "Prince Finn" that said he didn't like her just before they arrived at the Tree Fort.

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 from a bush at first saying she is 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 hurts her, causing Flame Princess to believe that Finn is intentionally hurting her. She leaves in a huff without allowing Finn a chance to explain, not recognizing his claims that he was not trying to hurt her were genuine.

After a brief chase, she concludes Finn is trying to impede her, causing her to decide to turn "this land" (starting with the Goblin Kingdom) into her own fire kingdom. She continues to set the kingdom and its citizens on fire apparently ignoring Finn's pleas for her to stop. When Finn realizes he cannot make her understand his feelings, he breaks down his fireproof suit and cries wishing he could "just like a girl." One of his tears falls onto the flames as she is leaving the ravaged kingdom, 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, but still glowing, and then leaves saying, "Bye, Finn." In "Burning Low," she and Finn start to date, sharing multiple hugs and eventually kissing. This results in Flame Princess' instability to activate, causing her to burn through the earth's crust and also causing Finn to dive in after her. When he reaches the bottom and finds her unconscious, he holds her in his arms and gives her CPR, causing her to wake up and rekindle. After being returned to the surface, they share a kiss with Finn kissing a rock and giving it to her; with her kissing the rock in return. The episode ends with the two walking off together, with Princess Bubblegum sighing and stating, "She's stabilized. We're safe... for now."

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. She recognizes Jake as "Sir Jake, Baron of the Grasslands" in his own words, and "Prince Finn's Buffoon" in the words of her father. She has not interacted with him directly, though she does seem to enjoy his song as well as the fact that he accidentally kills her father's jester by spilling water on him (though it should be noted she seems upset about it until Flame King says "I do hate my jester"). She doesn't seem to care that Prince Finn "killed" Jake, but is instead happy she has a young man to date. Jake does not interact much with Flame Princess in the show but in "Burning Low" Jake gives advice to Finn about dating showing that Jake has approved Finns new love interest. In "Burning Low," they seem to be friends, though they don't interact much in the episode.

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 idly whispered behind her back

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 colored and she wears a long tank top dress that touches the ground. She doesn't wear shoes, though her dress usually hides her feet from view. There is a red gem on her forehead and the middle of the chest of her dress. The two gems are similar to the many small gems that Flame King has on his armor suit. She has black eyes that sparkle white and yellow in the light of her fire as shown in the 3 screen shots 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 vary in size from about baseball-sized to larger than Finn, 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 "fly" 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 apparent pain. The fires that Flame Princess makes are a part of her, and stomping on or dousing the fire causes her pain.

She can travel quickly at a large distance by transforming into fire and moving to her desired area then return to original form.

She has an extremely unstable makeup. If her elemental matrix is exposed to extreme romance, she would sink through the earth's crust and set off a series of reactions that would cause a meltdown that would burn up the planet from the inside.

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. Based on this outburst and her imprisonment in the lantern, it is likely Flame Princess has a destructive nature, though it is possible her nature is a result of her imprisonment, or could be because she is a Fire Elemental, and "fire's purpose is to burn," as she states in Hot to the Touch. 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." 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 seems to be able to handle pain, illustrated when Finn jumps into the water while his foot is on fire, and 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.
 * Princess Bubblegum confirmed that she had Flame King imprison his daughter, Flame Princess, in a lantern because she was physically unstable and her elemental matrix can't handle extreme romance.
 * Flame Princess once referred to Finn as a Water Elemental because she saw him create water when he cries in "Hot to the Touch."
 * 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.
 * In the episode "Burning Low," Finn kissed Flame Princess three times, although the second kiss was to give her oxygen and the third was indirectly through a rock.
 * As of "Burning Low," Flame Princess and Finn are currently dating.
 * When Flame Princess transforms into her larger form, her face resembles that of her father, the Flame King.
 * Fire created by Flame Princess is connected to her on some level. When her fire is forcefully extinguished it causes her pain, but she can extinguish her own fire (seemingly without pain) as seen in "Hot to the Touch."
 * 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.