It could also be a corrupted version of one of Fionna's friends. For example, if Cake were to be turned evil by some dark magic. Cake would know all of Fionna's weaknesses and could use that knowledge against Finn in his Fionna form, making her a formidable and tragic antagonist.
One possible storyline could be Finn exploring the world as Fionna. He might have to deal with the different social dynamics in the female - dominated version of the Adventure Time world. Maybe he'll struggle to fit in at first but then find his own place among the characters like Cake and Prince Gumball.
It could start with Finn exploring a strange new area in his world and suddenly stumbling upon a portal. When he steps through, he finds himself in Fionna's world and right in front of her. There's an immediate sense of confusion and curiosity from both of them.
Cake is also very popular. Her unique ability to transform and her sassy personality make her a favorite. Many fanfictions explore her relationship with Fionna more deeply, like how she always has Fionna's back in tough situations.
One interesting plot could be Fionna and Cake going on a quest to save their world from a new, mysterious dark force. They might encounter strange new creatures and have to use their wits and friendship to overcome challenges.
Well, it's interesting because it gives a fresh perspective on the Adventure Time universe. Fionna and Cake are such unique characters, and the graphic novel delves deeper into their story. It might have new adventures, different relationships explored, and perhaps some new magical elements that are not as prominent in the original series.
One reason could be a change in her diet. If she starts eating more junk food like the sugary candies that are abundant in the Land of Ooo. For instance, if she befriends a candy - making gnome who gives her free samples all the time.
In Adventure Time, perhaps Fionna stumbles upon a magical food source that is super delicious but also really fattening. Every time she eats it, she gains a little more weight. At first, she doesn't really notice, but as it adds up, she has to face the reality. Her friends might be a bit concerned at first, but then they support her in finding a balance between enjoying the new food and staying healthy. She could learn some valuable lessons about self - care and moderation through this experience.
Definitely Prince Gumball. His relationship with Fionna can add a lot of drama and interesting storylines. Also, Ice King. He can be both a comical and menacing presence. And of course, Marshall Lee. He has his own unique charm and his interactions with Fionna are always exciting.