<P> "Fionna and Cake" is the ninth episode of the third season of the American animated television series Adventure Time . The episode was written and storyboarded by Adam Muto and Rebecca Sugar, from a story by Mark Banker, Kent Osborne, Patrick McHale, and series creator Pendleton Ward . It originally aired on Cartoon Network on September 5, 2011 . </P> <P> The series follows the adventures of Finn (voiced by Jeremy Shada), a human boy, and his best friend and adoptive brother Jake (voiced by John DiMaggio), a dog with magical powers to change shape and grow and shrink at will . In this episode, Finn and Jake are forced to listen to The Ice King's fanfiction about the gender - swapped Fionna (voiced by Madeleine Martin) and Cake the cat (voiced by Roz Ryan). In his story, Fionna goes on a date with Prince Gumball (voiced by Neil Patrick Harris) and fights the evil Ice Queen (voiced by Grey DeLisle). </P> <P> The concept of Fionna and Cake was based on sketches that series' character designer and storyboard revisionist Natasha Allegri made . Ward was pleased with her creations, and decided to canonize them . Originally, the episode did not feature the Ice Queen at all, and the middle part of the episode saw Fionna go on a date with Gumball to a restaurant; this subsequently changed . The episode was watched by 3.315 million people, making it--at the time--the most - watched episode of the series . "Fionna and Cake" received largely positive reviews from fans and critics alike . Two sequels to the episode--"Bad Little Boy" and "The Prince Who Wanted Everything"--were produced during the show's fifth and sixth season, respectively . </P> <P> Fionna and Cake are helping Prince Gumball decorate for the Biennial Gumball Ball when Gumball asks Fionna if she would like to go to it tonight with him . Their conversation is interrupted when the Ice Queen breaks into the castle and tries to kidnap Gumball . Fionna and Cake start to fight her before she mysteriously disappears . Gumball (who is apparently unharmed) arranges a date with Fionna . At the Tree Fort, Fionna and Cake argue over whether or not Gumball asked Fionna on a date . Cake decides to come along to help Fionna out . At the Castle Gardens, the two are met by Gumball and his steed Lord Monochromicorn . The group then flies through the air while Gumball serenades Fionna with the song "Oh, Fionna" and eventually asks her to be his girlfriend . When Fionna and Cake get to the ball, Prince Gumball takes Fionna to his room (decorated with candles and rose petals) and locks the door . She becomes flustered and backs away when he begins to take his shirt off . A drop of water lands on her shoulder, she looks up to see the real Prince Gumball trapped inside a giant icicle on the ceiling . The fake prince is revealed to be Ice Queen . Fionna is soon incapacitated; Cake senses trouble and rushes to her rescue . </P>

What episodes of adventure time are fionna and cake in