A possible main antagonist could be a corrupted version of Bellwether. After her time in prison, she could find a way to tap into the power of darkness. She wants revenge on Zootopia and uses the Heartless to cause chaos. She would be a devious antagonist as she already knows the ins and outs of Zootopia.
It could be a Heartless that has evolved in a unique way within Zootopia. This Heartless has the ability to manipulate the animals' minds and turn their fears and prejudices into weapons. It uses the natural hierarchy and diversity of Zootopia against the inhabitants, creating division and chaos, and it becomes the main threat that Sora and his new friends have to defeat.
Perhaps a new character, an ancient evil that has been sleeping beneath Zootopia. This entity wakes up due to some imbalance in the world of Kingdom Hearts. It starts to possess the animals and turn them into dark minions. It's powerful and its goal is to spread darkness across Zootopia and then to other worlds in the Kingdom Hearts universe.
One possible plot could be that Sora, Donald, and Goofy arrive in Zootopia. They discover a strange darkness spreading that is making the animals act out of character. Sora teams up with Judy Hopps and Nick Wilde to find the source of the darkness and save Zootopia. Along the way, they face challenges like solving mysteries in the different districts of Zootopia and fighting against the dark - influenced animals.
A sly fox from an old - fashioned fox gang could be the main antagonist. This fox might see the baby fox as a threat to their way of life or might want to use the baby fox's innocence for their own devious plans.
Sora would be an obvious choice as he has been the central character throughout the series. His journey doesn't end with the defeat of Xehanort, and there are still many things he could experience in the aftermath.
Sora would definitely be a main character. He's the protagonist in the Kingdom Hearts series, so it makes sense for him to be involved. The dalmatians themselves, especially Pongo and Perdita, could also be main characters. They could lead Sora through their world and help him understand their unique situation.
It could also be a new character created specifically for the fanfiction. This character could be from the world of the crossover and have some special ability or knowledge that helps in the fight against the Heartless. Maybe they have a deep understanding of the magic or technology in their world that can be used to counter the Heartless threat.
Captain Hook would be an obvious choice as the main villain. He already has a long - standing feud with Peter Pan in the original story. In a Kingdom Hearts fanfiction, he could team up with the Heartless or be influenced by the Darkness to become even more menacing. He could also be after the power of the Keyblade, thinking it would give him an edge over Peter and his friends.
A new character could be introduced as the main character. This character could be a native of the kung fu - inspired world in the crossover. They could be the one to teach Sora and his friends about kung fu, and then join them on their journey to fight against the darkness that threatens both worlds.
A character from a world of music could be a great addition. They could use musical notes as attacks or defenses. For instance, they could play a melody that heals allies or a discordant tune that stuns enemies. And a character who is a time - traveler from a world where time is in chaos. They could have the ability to freeze or speed up time in certain areas, which would add a whole new dimension to the battles and adventures in the fanfiction.
Well, obviously Kairi would be a likely candidate. She has a long - standing relationship with Sora. Then there's Xion, who has her own unique connection to Sora. Aqua could also be part of it as she is a strong and important character in the Kingdom Hearts series. Also, Namine could be included as she has interacted with Sora in many ways.
Sora is the central character in Kingdom Hearts story. He's the one who is on the quest to save the worlds. Donald Duck, with his magic, and Goofy, with his strength, are his companions. Riku is a character who starts off as Sora's rival in a way but later becomes an important part of the story as he battles his own inner demons. Kairi also plays a crucial role. She's often in danger, and Sora is driven to protect her, which is one of the driving forces of the story.