A power - hungry magician in the city could be the villain. He sees the Dalmatians as having some sort of magical essence that he wants to harness for his own dark magic. Penny, with her love for the puppies, has to figure out how to stop the magician's evil plans. She might seek the help of other friendly animals in the city and use their unique abilities to combat the magician's magic.
One idea could be Penny's adventures in the city before she meets the Dalmatians. Maybe she's on a quest to find a special item and her path crosses with the puppies by chance.
It could be a greedy land developer. He has plans to build a huge shopping mall on the land where the Dalmatians and their owners live. In order to clear the land, he decides to get rid of all the animals, especially the Dalmatians puppies which he sees as a nuisance. He sets traps and hires people to capture the puppies, making him a very menacing villain in the fanfiction.
A jealous show - dog breeder could be the new villain. He sees the Dalmatians getting all the attention and decides to plot against them. He tries to frame them for causing chaos at dog shows so that his own dogs can win all the prizes.
If Cruella was good, the main conflict of the story would disappear. The dalmatians would no longer have to fear being kidnapped for their fur. Instead, she might be a friend to the family, perhaps using her fashion sense to design cute outfits for the puppies.
Obviously, Lucky is one of the main characters. He's often the focus as the story is centered around him.
For character development, you could focus on the 102nd Dalmatian being an outcast at first. Maybe it has a different - colored spot or a unique behavior that makes the other Dalmatians hesitant to accept it. But as the story progresses, it shows great courage and loyalty, winning the others over.
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.
Well, apart from Cruella de Ville, the Dalmatian puppies play a major role. They are not just simple animals in the story but characters with their own charm. Their spots make them unique and desirable to Cruella. Then there are the owners of the puppies. These are the good - hearted individuals who care for the puppies as part of their family. They are the ones who will fight against Cruella's cruel intentions. There may also be some other minor characters like servants or people in Cruella's social circle who might be aware of her strange obsession but may or may not be involved in her schemes.
One idea could be that the jewel is a magical heirloom of the Dalmatian family. It has the power to protect them from the evil Cruella. The puppies go on an adventure to find the jewel when they sense Cruella's return.
In a fanfiction, Waddlesworth and Oddball could be the heroes of the Dalmatians. When the group of Dalmatians is in trouble, perhaps facing a new villain who wants to capture them all. Waddlesworth, with his cleverness, and Oddball, with her unique skills (maybe she can do something extraordinary because of her different genes), they team up to outwit the villain and save their Dalmatian family.