Obviously, Cinderella and the prince would be likely to be featured. They are the central characters of the original story, and any continuation would probably revolve around them and their relationship.
The step - sisters could also be important characters. Their relationship with Cinderella could be explored further. Maybe they have changed for the better or are still causing trouble in the new fanfiction.
Naruto himself is very likely to be featured. He's the main character after all.
Naruto is a very likely character. Given his rebellious nature and his history of being an outcast in some ways, it's easy to imagine a scenario where he gets caught up in something that lands him in prison. His determination to break free and his loyalty to his friends would make for an interesting story.
Percy Jackson himself, of course. And Annabeth Chase. They're like the main duo.
There could also be appearances from other characters like Smackle. Maybe she's initially uncomfortable with the idea of wearing a bikini but through her friends' support, she gains confidence and has a great time at a pool party or beach outing in the fanfiction.
Well, for sure Yugi would be in it. He has that special bond with the spirit of the Millennium Puzzle, and that could lead to all sorts of adventures in the world of The Ocarina of Time. Then there's Joey. His loyalty to Yugi and his own dueling skills could play a role. In terms of The Ocarina of Time characters, Zelda would likely be involved. She has her own powers and knowledge, and her interaction with the Yu - Gi - Oh! characters, especially Yugi, could be really interesting. And of course, Ganon could be a major antagonist in the fanfiction, causing trouble for both sets of characters.
Barbara Gordon could be a main character. She has connections to the Batfamily in multiple ways, and in the context of 'the art of love', her relationships, whether it's her friendship with Dick or her mentorship - like relationship with others, can be explored. Also, Damian Wayne is bound to be there. His growth within the family and his evolving understanding of love, especially considering his unique upbringing, would be interesting to see in this fanfiction.
Obviously, Harry Potter himself would be a central character. He's the main protagonist in the series, so it's likely he'd be involved in the Christmas - related events. Hermione Granger would also be there as she's Harry's best friend and loves to participate in all things magical and festive. Ron Weasley too, as he's part of the trio. Dumbledore might also make an appearance, perhaps guiding the students in some Christmas - themed activities or sharing some wise words about the season.
Sasuke would likely be featured. Since he and Naruto have a deep bond, Sasuke might be involved in Naruto's decision to retire or in filling the void left by him. Also, Naruto's family, like Hinata and his kids, would be important characters. They would be part of Naruto's post - retirement life, showing how they support him or how they are affected by his new lifestyle.
The songs in A Cinderella Story include 'Crash World' by Anna Waronker. Another one is 'Now You Know' by Hilary Duff. They both fit the theme and atmosphere of the movie perfectly.
Finn and Jake are bound to be main features. They've been at the heart of the series all along.