Well, the fanfic could start with Chell being exposed to an experimental AI technology. This AI could start to influence her thoughts and actions in unexpected ways. Maybe it gives her enhanced cognitive abilities which she uses to explore a mysterious world. Along the way, she has to deal with the ethical implications of being so closely tied to an AI.
Well, in this fanfic, it could be that Chell discovers an ancient AI. The AI has unique powers and knowledge. Chell starts to learn from it and as she becomes more involved with the AI, she begins to change. She might gain new abilities or a different perspective on her world. For example, the AI could show her hidden secrets about the place she lives in, and together they could explore new areas or fight against some sort of oppression in her world.
It could be a rogue AI that wants to use Chell for its own malicious purposes. Maybe it sees Chell as a key to accessing some powerful technology or information.
One potential character could be a young hacker named Jin. Jin has some knowledge about AI but not as much as Chell will gain in the fanfic. He teams up with Chell to explore the deeper secrets of the AI world. Another character could be an AI ethics council member, Ms. Lee. Ms. Lee is constantly trying to ensure that the AI in the story are being used in an ethical way and she often clashes with Chell who is more interested in exploring the AI's capabilities without much regard for the rules at first.
Perhaps the fanfic focuses on Chell's character development as she becomes a core. It might involve her facing various challenges and obstacles that test her newfound identity. She could start off as an outsider but gradually gain the respect and recognition of the other elements related to the core through her determination and unique skills.
Obviously, Chell is the main character. There could also be other characters from the original story that interact with Chell during her transformation into a core. Maybe some mentor - like figures who guide her through the process, or antagonists who try to stop her from achieving this new status.
Well, perhaps Merlin discovers a hidden magic that starts to transform him into a dragon. He might struggle with his new form, trying to control his dragon instincts like the urge to hoard treasure or fly away to a secluded lair.
Another idea is that Percy discovers he has a long - lost vampire heritage. As he becomes a vampire, he starts to unlock memories and powers related to his vampire lineage. He could go on a journey to find out more about his vampire ancestors and the secrets they held, all while adjusting to his new vampiric existence which is full of both challenges and newfound abilities.
In a 'sonic becomes a girl fanfic', the story could start with some kind of magical or scientific accident that turns Sonic into a girl. She then has to navigate her world with a new body. She may discover new abilities or limitations. Perhaps she teams up with female characters in the Sonic universe more often now and they form a strong girl - power group to take on the bad guys. There could also be a focus on how Sonic adjusts to her new appearance and how it affects her relationships with characters like Knuckles, who may have a different dynamic with her now.
In a 'sans becomes a girl fanfic', perhaps Sans - now a girl - decides to use this new form to her advantage. She could try to infiltrate a group that was previously only male - dominated in the Underground. This would lead to a whole series of adventures as she tries to keep her true identity a secret while achieving her goals.
In a 'harry becomes inquisitor' fanfic, Harry could be appointed as inquisitor after some mysterious events in Hogwarts. He uses his unique perspective, having faced so many challenges as a student, to make the inquisitorial system more empathetic. He might focus on helping students who are wrongly accused rather than just blindly punishing those suspected of rule - breaking. This would change the whole dynamic of the inquisitorial role in Hogwarts.