Fionna

Fionna (previously named Fiona) is the gender-swapped version of Finn, created by series designer Natasha Allegri. She is usually seen in the company of her own stretchy companion, Cake who is the gender-and-species-swapped version of Jake. Fionna's enemy is the gender-swapped version of Ice King, the Ice Queen. It was revealed on April 6, 2011 that the working title of the sixth episode in season three is "Adventure Time with Fionna and Cake."

Appearance
She sports an outfit similar to Finn's: a rabbit-themed hood (opposing Finn's bear-themed hood), exposed locks of blonde hair. Unlike Finn, she has her neck and upper chest area exposed, she also has a sky blue shirt with longer sleeves than Finn's, and a dark blue skirt, which are a lighter shade of blue than Finn's clothing, the same green backpack, athletic socks that have two blue stripes at the top, and Mary Jane shoes. Like Finn, she occasionally wears a yellow sweater when she is in the Ice Kingdom. While Finn had a sword made out of gold, Fionna has a sword made out of ruby. It should be noted that she has a much thicker, curvier figure than most other humanoid females seen in the show (save Susan Strong), with wider hips and thicker legs. This could be a reference to her status as a warrior, or a device to greater show gender differences between her and Finn. Natasha refers to this as "chubby cute".

Trivia

 * Her name was officially changed from "Fiona" to "Fionna," presumably to make it more similar to Finn's name.
 * Similar to Finn and his cracking voice, Fionna also seems to be going through puberty as shown in "PMS Time with Fionna and Cake"
 * Fionna is the only other known human besides Finn seen in the Adventure Time series. It is unknown if she lives in the Land of Ooo like Finn, the same time period as Finn, or in a separate universe.
 * Fionna has a ruby sword, as opposed to Finn's gold sword.
 * Like Finn and his crush on Princess Bubblegum, it is revealed in many portraits posted that Fionna has a crush on Prince Gumball.
 * Similar to the way Finn has missing teeth, Fionna has buck teeth like a rabbit.
 * Cake's parents may have adopted Fionna since Jake's parents adopted Finn.
 * Revealed on Natasha Allgeri's formspring account, the dress she designed for Fionna is based off Princess Serenity's dress from the anime show Sailor Moon.