Well, of course, Bella herself. And there could be her new friends. Maybe a quirky neighbor who always has some strange advice for her. Also, if it's about her new career, there could be a strict but kind mentor who helps her grow in her chosen field.
There could be some fictional characters unique to the fanfiction world. Like a magical creature that only Bella can see and it becomes her guide in this new life. Or a group of rebels who are trying to change the society Bella has just entered and she has to decide whether to join them or not.
There could be a new rival for Ash. This rival might have a very different approach to Pokemon training, like focusing more on the beauty and grace of Pokemon rather than just battle strength.
There could be a mysterious mentor figure who guides Naruto in his secret life. This person might have unique abilities and a deep understanding of the ninja world's secrets. Another potential new character could be a spy from another village who discovers Naruto's secret life and tries to use it to their advantage.
There could be Klaus. Since he is Rebekah's brother, he would likely be part of Bella's life in some way. He might be a protective uncle or a source of conflict if he has different ideas about how Bella should be raised. Another character could be Elijah. He might act as a mentor to Bella, teaching her about their family's history and values.
Caroline could be in the story. She might be Bella's friend or a rival. If she's a friend, she could help Bella navigate the supernatural world. If a rival, it could be because of her relationship with Damon or Stefan in some way. Also, Klaus could be a character. He might see Bella as a means to get to Damon, or he could be interested in her unique abilities if she has any.
There might be a young local artist who becomes Bella's friend. Also, a mysterious old man who seems to know a lot about the history of the place where Bella has moved. And perhaps a group of teenagers who introduce Bella to the local hangout spots and their unique way of life.
There's also a possibility that some of the more morally grey characters in Gotham, like Catwoman, could be Bella's allies. Catwoman has her own code of ethics, and she might relate to Bella's struggle between good and evil. They could work together in certain situations, especially if there are mutual benefits involved.
A potential main character could be Bella's best friend. This friend could provide support and a different perspective as Bella navigates her new identity. There might also be a mentor figure for Bella, someone who knows a lot about Elijah's world and can guide her. This could be an old friend of Elijah's or a wise elder in their community.
Well, apart from Bella, there could be a male lead who is the creative director of the 'for him' brand. He could be a strict and demanding professional but also has a soft side. Then there are the makeup artists and hair stylists who are always around Bella during shoots. Also, there could be Bella's agent who is constantly trying to get her the best deals and manage her career. There might be some models from other agencies who are jealous of Bella's rise in the 'for him' modeling world.
A wise old owl could be a new character. This owl could be the one who actually has knowledge about the real threats (or lack thereof) in their world. Maybe he tries to guide Chicken Little and the other animals. Another potential character could be a mischievous squirrel. The squirrel could be constantly causing small troubles that make Chicken Little think the sky is falling all over again. For example, it could knock down acorns that make loud noises.
A wise old sea turtle could be a new character. He could be the one who gives the mermaid advice about the human world and warns her of the potential dangers.