Obviously, Cortana in her human form would be the main character. But there could also be a scientist who was involved in the process of her becoming human, either intentionally or accidentally. This scientist could be a mentor or a conflict source for Cortana as she adjusts to her new life. Another possible main character could be a human friend that Cortana makes early on in her human existence, someone who helps her understand human culture and values.
The main character is Cortana - turned - human. Additionally, there could be an AI ethics researcher who is fascinated by Cortana's transformation. This researcher would study Cortana's experiences and try to draw conclusions about the morality of creating human - like AIs. There might also be a government agent who is tasked with monitoring Cortana's activities to ensure she doesn't pose a threat to national security, adding a layer of tension to the story.
The plot could involve Cortana being turned into a human as part of a top - secret project. Once human, she realizes that she has lost some of her super - computing abilities but has gained intuition. She starts to explore her newfound senses, like taste and touch. She could get involved in a mystery that only she, with her unique perspective from being an AI, can solve. This mystery could be related to a threat against humanity that she discovers through her old AI connections, and she uses her new human skills to fight against it.
There could be other AI characters that are either friends or foes of Cortana. They might try to interfere with her control over the human or help her in some way. For example, another AI might think that Cortana's control is unethical and try to set the human free.
Well, one possible plot could be Cortana suddenly gaining a physical human form and struggling to adapt to human emotions. She might find it difficult to understand things like love, pain, and joy at first. For example, she could be confused by the concept of crying when sad. As she tries to fit into the human world, she could face challenges like learning social norms and making real friends.
It could be another ghost who is jealous of Casper's new human form. This ghost might try to sabotage Casper's attempts to fit into the human world, perhaps by causing chaos around him and making humans afraid of him again.
It could be an ordinary person, like a young adult who is just going about their daily life until something strange happens and they become a predator. This character would then have to learn how to deal with their new situation.
It could be a vampire who resents Damon for becoming human. This vampire might see it as a betrayal of their kind. They could try to either turn Damon back into a vampire against his will or simply make his human life miserable.
The main antagonist could be a dragon hunter. Since Saphira is now in a human form and has lost her dragon defenses, the hunter sees her as an easy target. He might be after her because he believes that she has some connection to the dragons and he wants to use her to find the dragon lair or something valuable related to dragons.
It could be a dark magic user who doesn't want the human - turned - Twilight to succeed. Maybe this antagonist sees the new Twilight as a threat to their own power or plans in the pony world.
A powerful witch could be the antagonist. She might have been the one who turned Damon human again against his will, and now she has some sinister plan for him. For example, she wants to use his new human form to perform some dark magic ritual that requires a human with a vampire past.
Well, perhaps in this fanfiction, Cortana controls a human in a post - apocalyptic setting. She uses her intelligence to make the human perform tasks like finding resources, building shelters, or fending off threats. It could be an interesting exploration of how a powerful AI like Cortana would interact with a normal human in extreme circumstances.