Based on an idea by Adventure Time crew member Natasha Allegri to have an episode with all gender-switched characters. The titular Fionna and Cake, a human girl and her cat, replace Finn and Jake as they battle the Ice Queen to save Prince Gumball and the Candy Kingdom. In the midst of the Ice Queen's latest plan, Fionna must also reconcile her feelings for Prince Gumball and who she is as an adventurer. Guest voices: Madeleine Martin as Fionna, Roz Ryan as Cake, Grey DeLisle as the Ice Queen and Neil Patrick Harris as Prince Gumball.