Through some strange occurrence involving time and space, Fionna finds herself dealing with some alternate versions of her.

Shoko: One of her previous incarnations

Penelope: An incarnation of her from the distant future. Penelope was shown a couple of times in the Adventure Time comics, though nothing has been elaborated on much outside of the fact that she’s a future incarnation of Finn

Lynn: Lynn the Person, who alongside Janet the Fox are characters that exist in Ice President’s fanfiction based off ‘Flynn the Human Being’ and ‘Jacques the Raccoon’. These three are, in turn, part of Ice Queen’s fanfiction based on Fionna and Cake, who, of course, are part of Ice King’s fanfiction.