Billy Abbott could be an interesting addition. He could bring some outside drama, perhaps through a business deal or some personal vendetta against Adam. His flamboyant personality would contrast with Adam and Chelsea's relationship and add an element of chaos to the fanfiction.
Maybe they could go on a road trip together. Along the way, they discover new things about each other and their pasts. They might run into old friends or foes from their respective storylines, which could add drama and conflict to the fanfiction. For example, they could encounter someone who has a grudge against Adam and Chelsea has to decide whether to stand by him or not.
Obviously, Adam himself is a must - include. His character has a lot of depth and potential for further development. Also, his mother would be great to include as she plays an important role in the story. And the villain from the movie could be brought back in a new and more menacing way.
Riko could be a great supporting character. As the coach, she can play a role in bringing Hyuuga and Kuroko closer. For example, she might assign them special tasks together which force them to interact more. Also, Kagami could be included. His competitive nature and his friendship with Kuroko can add an interesting dynamic. He might be initially jealous of Hyuuga's relationship with Kuroko, but then come to understand and support it.
The enchanted objects in the castle like Lumière and Cogsworth would be great. They add humor and charm to the story. Also, Gaston could be included in a different way, like he has a change of heart and tries to help them. And Belle's father could also be a key character, perhaps he discovers something important about the curse.
Polly could be a great supporting role. Since she has a history with Piper, she could bring in some family - related drama. Also, Red would be an amazing addition. Her motherly nature towards Piper in prison could translate into her being a sort of mentor or a source of advice in their married life.
Haley would be a great supporting role. She could offer Peyton advice on pregnancy based on her own experiences. Lucas could also be included, perhaps he helps Nathan with getting ready for the baby, like fixing up a room in their house. And Brooke, she might be the one to throw a baby shower for Peyton and bring in all the fun and glamour to the story.
Renji could also work well. He's always been in the thick of things in the Soul Society. His rough - around - the - edges personality could contrast with the more subtle relationship between Ichigo and Lisa. He might be the one who accidentally stumbles upon their budding relationship and gives some comical reactions.
Definitely include Natsu. His enthusiasm and positive energy can add some light - hearted moments to the story. He could also be the one to accidentally push Cana and Gildarts closer together, like by getting them into a situation where they have to rely on each other. Lucy would also be a good addition. She's a good friend to Cana and can offer a different perspective on love and relationships, having her own experiences in the guild.
Rock Lee would be an exciting supporting character. His energetic and determined personality could bring some humor and motivation to the story. He could challenge Naruto to friendly sparring matches, which in turn could make Ino and Sakura cheer for them. Choji is also a good option. His loyalty to Ino and his friendship with Naruto could create some heartwarming moments. And Tsunade could play a role as well. As the Hokage, she could assign them important missions and also be a mentor figure, especially to Sakura, which would impact the relationship between Naruto, Ino, and Sakura.
Kakashi would be an interesting addition. He could act as Naruto's advisor in matters of the heart. Since Kakashi has a good understanding of Naruto's character, he could give Naruto some valuable insights on how to handle his relationship with Shizune. At the same time, Kakashi's calm and collected nature could contrast with Naruto's more impulsive self, making for some engaging interactions within the fanfic.