Obviously Percy himself. Also, Annabeth would probably be there as his girlfriend. Grover, his satyr friend, might also make an appearance. And the gods, like Poseidon, Percy's father, would surely play a role, either guiding Percy or testing him on his path to godhood.
The main character Percy is a given. Chiron, the centaur trainer at Camp Half - Blood, could be there to give Percy advice. Nico di Angelo might be involved too. He has his own connections to the underworld and could be a valuable ally or a source of conflict. And let's not forget Tyson, Percy's cyclops half - brother. His unique strength could be helpful to Percy in his journey to becoming a god.
Obviously, Percy and Annabeth are the main characters. But we could also see some of their demigod friends like Grover. Grover might stop by to check on them and end up getting involved in the babysitting chaos. Maybe Chiron could also make an appearance, giving Percy and Annabeth some advice on how to handle the kids.
Obviously, Rarity herself is the central character. Her friends from the Mane Six, like Twilight Sparkle, who could help her understand the magic involved in becoming an alicorn. Also, Spike might be there, as he's always around Twilight and could play a role in Rarity's journey, perhaps by providing some useful information he's found in his library duties.
Obviously, Percy himself would be the main character. Annabeth would most likely be there too, as she is an important part of Percy's life. Grover would also be a likely character, being Percy's best friend.
Obviously, Percy Jackson himself. Then there would probably be Annabeth, his girlfriend. She could be either supporting him in his new role or be a bit skeptical at first. Grover might also show up, providing some comical relief and maybe some sage advice from his nature - centric perspective. Other gods like Aphrodite would surely be there, either causing trouble or trying to manipulate Percy for her own purposes.
Obviously Percy himself. And likely his friends like Annabeth. She would probably play a role in either helping him adjust or trying to find a way to reverse the situation if Percy doesn't want to be a god.
Annabeth would most likely be his ally. She has been with him through thick and thin, and her wisdom would be invaluable as Percy becomes a god. Grover could also be an ally, using his nature - related powers to help Percy in different situations. Another possible ally could be Nico di Angelo. With his control over the dead, he could provide unique assistance, especially when it comes to dealing with the darker aspects of the godly world.
The main character is Kobayashi. There could be a magical creature or wizard who accidentally caused her transformation. There may also be a group of adventurers who cross paths with her. Some of them might be curious and want to help, while others might be scared and try to avoid her. And of course, there could be a love interest, perhaps another dragon or a human who is attracted to her new and unique self.
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, there could be new characters created specifically for this fanfiction. For instance, Chaos might have his own loyal servants or minions who interact with Percy. There could also be other heroes or demigods from different pantheons. They might come to Percy for help or to challenge him. And of course, Percy's mother, Sally. She might be worried about her son and try to reach out to him, even though he is now in the realm of Chaos. Her presence could add an emotional aspect to the story as Percy has to balance his new life with his love for his mother.
The Hunters of Artemis are very likely to show up. They are Artemis's loyal followers and would surely be involved in the search for their mistress. Annabeth could also be there. She's Percy's friend and has great wisdom, which could be useful in devising a plan to save Artemis. Grover might be another character. His ability to sense things could help in tracking Artemis or finding clues about her whereabouts.