Season synopsis
Contains spoilers for this season and earlier seasons.
The fifth season begins where season four’s portal cliffhanger stops. Finn and Jake reach Prismo’s time room and learn that the Lich has wished for all life to end. Finn wishes that the Lich had never existed and is sent to Farmworld, where he is an ordinary boy living with his family and dog. He finds Simon Petrikov’s skeleton and the ice crown, then puts it on to help his family. Its power corrupts him; Jake becomes a Lich-like creature in the resulting disaster. In Prismo’s room, Jake changes the Lich’s original wish to sending Finn and Jake home, restoring Ooo. Finn remembers none of Farmworld, while Jake does.
The season also changes Finn’s relationship with Flame Princess. In “Frost & Fire,” Finn arranges fights between her and the Ice King because he wants to repeat a dream; when Flame Princess learns he manipulated them, she breaks up with him and leaves the Ice Kingdom in ruins. Later stories take the pair through separate challenges rather than undoing that breach of trust. At the other end of the season, Finn finds Billy’s unfinished bucket list and completes its remaining tasks as a tribute to the hero. He gives Canyon, Billy’s former partner, one last motorcycle ride and faces his fear of the ocean. Billy then appears and tells Finn that his biological father is alive; the final image points toward the Citadel, leaving that discovery for the next season.