|Relatives||Cake (Adoptive sister)|
|Introduced in||Animated short|
|Voiced by||Madeleine Martin|
While usually appearing as black dots, her eyes are seen as blue when enlarged. She wears a rabbit-themed hat with exposed locks of blonde hair and also has teeth missing in a similar fashion to Finn. Unlike Finn, her neck and blonde hair are shown. When she is not wearing her hat, her hair goes down to between her knees and ankles. Her outfit includes a teal blue shirt with elbow-length sleeves, a dark blue skirt, and knee-high socks with two thin, light blue horizontal stripes at the top. Fionna is a heavier set than Finn (which Natasha referred to as "chubby cute"). She has a green backpack and Mary Jane shoes.