Mainly, it's Cat Noir and Ladybug. Cat Noir, with his charm and acrobatic skills, is the one who gets hold of Ladybug's Miraculous. This action sets the story in motion. Ladybug, with her intelligence and leadership, will be at the center of the story too. She might be in a state of shock or determination to retrieve her Miraculous. Additionally, characters like Tikki and Plagg, the Kwamis of Ladybug and Cat Noir respectively, could also be important in the fanfiction as they are closely related to the Miraculous and can influence the actions and decisions of the two main characters.
One possible plotline could be Cat Noir finally confessing his true feelings to Ladybug while having her Miraculous. He might struggle with the newfound power and the responsibility that comes with it. Another could be them teaming up in a more equal way than in the original, sharing their secrets and working together to face a greater threat.
One consequence could be a power imbalance in Paris. Since Ladybug's Miraculous is crucial for maintaining the balance against evil. If Cat Noir takes it, he might not be able to use it as effectively as Ladybug, leading to potential chaos as Hawkmoth could take advantage.
Definitely Tikki and Plagg. These Kwamis are essential to the Miraculous universe. Their interactions with Cat Noir and Ladybug, as well as their own little quirks and personalities, can make for really fun fanfiction. Additionally, Sabrina, Chloe's sidekick, can be an interesting character to include. She could have her own story of breaking free from Chloe's control or getting involved in the hero - villain drama in some unexpected way.
No. In the normal 'Miraculous' series, Cat Noir is a superhero, not a criminal. Fanfiction might deviate from the original, but the general perception of his character is heroic. So, just because it's a fanfiction doesn't mean he's a criminal.
Ladybug and Cat Noir themselves are obviously very popular. Marinette (Ladybug) and Adrien (Cat Noir) have complex personalities and their relationship is full of potential for fanfiction. Tikki and Plagg, their Kwamis, are also great to include. They can add humor and also provide important insights into the Miraculous lore. Then there's Alya, Marinette's best friend. She can be a great supporting character, either helping Ladybug or getting into some comical misunderstandings.
Ladybug and Cat Noir themselves are very popular. Writers often like to explore their relationship further, whether it's developing their romantic feelings or their friendship as superheroes. Marinette and Adrien, their civilian identities, are also commonly included. Fans enjoy writing about their everyday lives and how they balance that with their superhero duties.
The storyline could progress with Cat Noir initially being excited about having both Miraculouses. He might try to show off his newfound power, but quickly realizes that it's not as easy as he thought to handle both at once.
Hawk Moth could still be the main villain. He might target Tom specifically because of his relationship with Marinette (Ladybug). Maybe he thinks that by akumatizing Tom, he can get closer to getting Ladybug and Cat Noir's miraculouses.
It could still be Hawkmoth. Since he's always after the Miraculouses, he might find a way to turn Cat Noir evil and use him as a tool to finally get Ladybug's Miraculous. So Hawkmoth would be pulling the strings in the background while Cat Noir does his dirty work.
There's a fanfiction called 'The Miraculous Origins'. It delves deeper into the backstory of the Miraculous. It explores how the Miraculous were created and how they came to be in the hands of the current holders. It's a long read but worth it for fans who want to know more about the lore of the Miraculous Ladybug Cat Noir universe.