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 Jake serenading Flame Princess Added by Breathe Tomorrowwith 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. In Burning Low, they seem to be friends, though they don't interact much in the episode.
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. Finn meets Flame Princess in "Incendium." Added by Breathe TomorrowIn "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 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 all he does is cry all the time. She comes to the conclusion that they are opposite elementals and that even if they like each other they can never be together. 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' instablility 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 unconcious, 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.
In the dream world induced by Worm King in "King Worm", Flame Princess claims to be his wife, as does Princess Bubblegum.
in "The Powerpuff Girls Crossover", Grievous is trying to be nice to her. He told Finn about Flame Princess. Finn told him that his armer is fire proof.