Well, you could have a fanfiction where the umbrella is a key element in a time - traveling adventure. For example, Ladybug and Chat Noir find an old umbrella that transports them to a different era in Paris' history. Or perhaps an akumatized villain uses umbrellas to spread his or her power, and Ladybug and Chat Noir have to find a way to counter this by using the unique properties of Ladybug's own umbrella. Also, it could be that the umbrella is a portal to another dimension, leading to a whole new set of challenges and adventures for our heroes.
One idea could be a story where the Peacock Miraculous has a unique malfunction that causes it to create unexpected akumas. For example, instead of creating the usual villains, it creates akumas that have the power to spread positive emotions but in a chaotic way that still disrupts Paris. Another idea is a fanfiction where the holder of the Peacock Miraculous has to team up with Ladybug and Chat Noir to fight against an ancient evil that is specifically drawn to the power of the Peacock. This could involve exploring the history of the Miraculous and its connection to this new threat.
Well, you could write a fanfiction where Edendaphne has to team up with a new character. They could have different personalities and powers, which would lead to some interesting conflicts and resolutions. For example, if the new character is really impulsive and Edendaphne is more cautious. Also, you could show how Edendaphne deals with the challenges of keeping her identity a secret, just like Ladybug and Cat Noir do.
You could write a fanfiction where there are new Miraculous holders. Imagine a character who discovers a long - lost Miraculous and has to learn how to use it. This new character could team up with Ladybug and Chat Noir, or they could start out as an antagonist because they misuse the power at first. Their journey of learning to be a true hero or villain could be really engaging.
A cool concept for Miraculous Ladybug fusion fanfiction could be a time - travel related fusion. Imagine Ladybug fusing with a past version of herself. This would bring about a character with double the experience and different perspectives on how to use the Miraculous. They might be able to come up with new strategies to defeat Hawkmoth that neither the present nor the past Ladybug could have thought of alone.
One idea could be that Marinette gets isekaied into a magical realm where the Miraculous have different powers and she has to learn to adapt quickly. Another could be that Adrien is sent to a parallel world through an isekai event and he meets alternate versions of his friends and enemies.
One idea could be a dance competition in Paris where Marinette and Adrien are secretly the superheroes. They use their super - agility and grace in the dance, which surprises everyone. Their opponents think they are just normal kids but they show extraordinary skills. Maybe there could be a villain who tries to disrupt the competition by using some dark magic related to the dance floor.
A crossover with the world of Sailor Moon would also be cool. The Miraculous holders could meet the Sailor Scouts. They could exchange their powers and fighting techniques. For example, Ladybug could show Sailor Moon how to use her yoyo in a more strategic way, and Sailor Moon could teach Ladybug about the power of love and friendship in her battles.
One idea could be that Hawk Moth frames Ladybug by creating false evidence of her causing chaos in Paris. For example, he uses his akumas to create illusions of Ladybug stealing or attacking civilians, which makes the public turn against her. Another idea is that a new villain frames Ladybug and Chat Noir by hacking into the media systems and broadcasting doctored footage of them doing bad things.
You could also write a fanfiction where the magic in the Miraculous Ladybug universe somehow gets intertwined with the magic in the Descendants' universe. Maybe the Miraculous themselves are affected by the dark magic from the Isle of the Lost, causing unexpected powers and challenges for Ladybug and Chat Noir as they deal with this new threat while also trying to keep their identities secret.
A more light - hearted idea could be that Tikki and Plagg get curious about the spirit world in the Avatar universe. They drag their holders, Marinette and Adrien, into an adventure in the spirit world. There, they meet various spirits that are similar to kwamis in some ways, and they have to solve a mystery that is threatening the balance between the spirit world and the human world.