Come Along with Me.In the distant future, Shermy (voiced by Sean Giambrone) and Beth the Pup Princess (voiced by Willow Smith) run around in what remains of Ooo. They find Finn's robotic arm and bring it to the King of Ooo, who turns out to be BMO. The robot tells them about the Great Gum War; before the war begins, Finn and Jake try to convince Princess Bubblegum to reconsider after they see King Man, Betty and Maja placing a spell. Marceline questions PB's motives, but Gumbald's spying drives her forward. As the battle is about to begin, Finn has another idea and he, Jake, PB, Gumbald and Fern unsuccessfully try to have a civil discussion. Jake tosses the nightmare juice from "Orb", and they are knocked unconscious. In the dream world, Gumbald abandons Fern (who begins fighting Finn) and tries to wake up but is stopped by PB. Gumbald and PB switch places, and begin seeing things from each other's perspective. Fern refuses to believe that Finn has suffered; Jake ventures into Finn's subconscious to fetch his vault, and Fern realizes that he and Finn are similar. Finn destroys the grass demon, freeing Fern from its influence while PB and Gumbald make up. They wake up, but Aunt Lolly transforms Gumbald with the dumdum juice because he "was never the epiphany type". As they settle on two candy kingdoms, a worried King Man arrives with GOLB following. GOLB sends his monsters to attack the heroes and King Man tries to get the Ice King to talk to Betty, who is in a trance. Betty's rude awakening makes Maja explode; she and the Ice King are eaten by GOLB, with Finn jumping in after them and losing his robot arm. As they are digested, the Ice King becomes Simon and he and Betty make up. The heroes battle the monsters and an infected Gumball Guardian, with Marceline transforming into a giant beast and taking down one of them. Afterwards, she and PB confess their love for each other and kiss. Everyone else is critically injured, leaving Jake to try to take down the Gumball Guardian; he is too late to save the treehouse. BMO consoles Jake with a song; they discover that the song's harmony repels and weakens GOLB and his monsters, and they get everyone to sing. Inside GOLB, Finn, Simon and Betty hear the song as it forms an exit; Betty remains behind when the Ice King's crown activates. Although she tries to wish GOLB away, she instead wishes for Simon to be safe. Outside, everyone watches as the monsters disappear and GOLB assumes a humanoid form and leaves. Fern finally disintegrates and Finn plants his seed at the remains of the treehouse, where a new tree immediately grows. BMO finishes his story, as Shermy and Beth leave and realize that they know where the Fern tree is. The Music Hole sings the show's ending theme, "Come Along with Me", while a montage of all the characters (and their fates) is shown. Interspersed throughout the montage are shots of Shermy and Beth climbing the tree; when they find the Finn Sword they recreate the familiar Finn-and-Jake pose from the show's title card, concluding the series.