Kaichou could be a great addition. Since she has a thing for Usui, her presence could create jealousy and drama. If she sees Usui getting closer to Yukimura, she might try to interfere. Another character could be a new transfer student who is really charming and tries to win over Yukimura, making Usui feel a bit possessive.
I think Hinata could be a great addition. He could be the comical sidekick who always gets into funny situations and in the process, either helps or hinders Usui and Ayuzawa's relationship. Another good character could be Ayuzawa's mother. Her presence could add some family drama, like she might not initially approve of Usui for her daughter.
A fanfiction where they swap personalities. Usui becomes more reserved like Yukimura usually is, and Yukimura becomes more confident and flirty like Usui. This change in their characters causes chaos at first but then they start to see the world from each other's perspectives and it deepens their relationship.
Pepper Potts could be a great addition. If she's initially hesitant about Tony taking on Peter as a sort of surrogate son, it can create a lot of drama. Maybe she's worried about the danger Peter could bring into their lives. Another good character is Happy Hogan. He could be the voice of reason, sometimes agreeing with Pepper, other times seeing the potential in Peter and siding with Tony. This can lead to some interesting arguments between the characters.
Ace is a great character to include. He was Whitebeard's adopted son, and their relationship was very deep. Stories about their interactions, whether it was Ace learning from Whitebeard or them having father - son moments, are always interesting. Marco is also a good choice. As Whitebeard's right - hand man, he could be in stories that show the inner workings of Whitebeard's crew and how they strategize and operate. Another one could be Luffy. Since Luffy had a connection with Ace and later respected Whitebeard, a fanfiction could explore their interactions.
Obviously, Bahubali himself is a must - include. His strength, courage, and leadership make him a central figure. Then there's Kattappa. His loyalty and his complex relationship with Bahubali can add a lot of depth to the story. Also, Devasena is an important character. Her love for Bahubali and her own strength as a princess can bring in elements of romance and female empowerment in the fanfiction.
The Warrens could be great characters to include. Their knowledge of the occult and their experience with haunted objects like Annabelle can add a lot of depth to the story. They can be the ones trying to either save Annabelle or stop her from causing more harm.
Obviously Chowder himself is a must - include. Mung Daal, as his mentor, also makes for great content. And Truffles, with her strict but caring nature, can add interesting dynamics to the story.
Definitely Lucius Malfoy. Since he is Draco's father, his influence on Draco could create internal conflict for Draco. If Lucius is against Draco saving Harry, it adds a whole new layer of drama. Bellatrix Lestrange is another good choice. Her insane and violent nature could pose a direct threat to Harry and make Draco and Blaose's task of saving him even more difficult. And don't forget Ginny. If Ginny has feelings for Harry and sees him getting closer to Draco or Blaose in a romantic way, it would cause a lot of jealousy and drama.
For a more unique take, including Jiraiya could be great. His pervy but knowledgeable personality could lead to some humorous and yet useful moments. He might have some ancient knowledge about the connection between the Naruto world and the Pokémon world where Darkrai comes from. On the Pokémon side, Cynthia could be a great addition. As one of the strongest Pokémon trainers, she could offer a different perspective on Darkrai and also help in battles against any enemies that might be using Darkrai's power for evil.
Obviously, the clone troopers themselves are essential. Characters like Rex, Cody, and Fives are very popular. Jedi generals like Anakin Skywalker and Obi - Wan Kenobi also make great additions as they often lead the clone troopers into battle. Then there are the villains. General Grievous can be a great antagonist in a Clone Trooper fanfiction as he is a fearsome enemy who the clones often face.