Fionna is the genderswap counterpart of Finn the Human on Adventure Time in the episode "Fionna and Cake". She is Prince Gumball's girlfriend, Cake's adoptive sister and Raina's daughter-figure. She is a 14 year old girl who has long blonde hair covered by her bunny hat except for one part, black beady eyes and she wears a blue shirt, a dark blue skirt, white socks and black shoes. She is voiced by Madeliene Martin.
Fionna lives in teh land of Aaa with Cake, her sister. She fights off the Ice Queen and dates Prince Gumball, who has a crush on her back. She manages to save Prince Gumball a couple of times in the past. Fionna also revealed to be friends with Marshall Lee who has a crush on her and she gets mad at him when he captures Cake. Although she was a fanfiction character by the ICe King who also has a crush on her and dreams of making her and Cake real.
She first appears in "MCF: Key to the Path" where she and Cake are sort of the Altivo role, but they play along with Raina and Jessy in their adventure.
- Like Finn, even though Fionna and Raina are not related and are the same age, Fionna still treats Raina like she's her mother.
- In Key to the Path, Discord refers to Fionna as Finn the Human's...twin sister. This is a joke because Finn and Fionna are counterparts to one another.
- The dress Fionna wore in her debut episode is simular to Princess Sailor Moon's dress.
- Her date with Prince Gumball and when he sings "Oh Fionna" to her is simular to "A Whole New World" from "Aladdin"
- MCF: Key to the Path(debut)