One idea could be that Hawk Moth is behind the kidnapping. He might have discovered Marinette's identity as Ladybug or suspect her. He could use her to try and get the Miraculous. Maybe he offers a trade to Chat Noir, the Ladybug Miraculous for Marinette's safe return.
In a fanfiction scenario, perhaps an akumatized villain kidnaps Marinette because they see her as a rival for someone's attention. For example, if there's a new girl in school who likes Adrien and she gets akumatized. She might think that by getting rid of Marinette, she can have Adrien all to herself. So, she kidnaps Marinette and holds her captive in some strange location, like an abandoned building.
Another possibility is that an unknown group from outside Paris discovers the power of the Miraculous. They manage to figure out that Marinette is connected to it in some way. So, they kidnap her to study her and try to find out how to get the Miraculous for themselves. This could lead to Chat Noir having to search for her all over the city and even outside of Paris, facing many challenges along the way.
A really interesting fanfiction idea could be that Lila and Marinette switch personalities for a day. This would be a comical yet thought - provoking situation. Lila would have to deal with Marinette's responsibilities and kindness, while Marinette might struggle with Lila's devious ways. It could lead to both of them having a new perspective on each other.
If Marinette was kidnapped, Tikki could be a key factor. She might try to communicate with other Kwamis to get help. Since the Kwamis have some special powers and knowledge, they could work together to find Marinette. For instance, Plagg could use his Cataclysm in a unique way to break through any barriers that are keeping Marinette captive.
One idea could be that Marinette vomits due to extreme stress. Maybe she's facing too many akuma attacks in a short time and the pressure gets to her physically. Another could be related to a strange side - effect of using the Ladybug Miraculous. For example, if she overuses her powers in a short period, it might cause some sort of physical reaction like vomiting.
One possible scenario could be that Marinette gets injured during a fight as Ladybug and is rushed to the hospital. In the fanfiction, her friends might come to visit her, and there could be some sweet moments between her and Adrien as he's worried about her. Maybe she has to keep her identity a secret even while in the hospital, which adds an extra layer of tension.
There's also 'The Luka - Marinette Connection'. In this fanfiction, the connection between Luka and Marinette is explored on a deeper level. It starts with Luka noticing Marinette's little quirks and how she tries to hide her feelings. As the story progresses, they start to open up to each other more. The author creates a really engaging story by adding in some mystery elements related to the Miraculous and how it might affect their relationship.
One great fanfiction could be about Marinette getting the Peacock Miraculous in a unique situation. For example, in a world where all the Miraculouses are scrambled among the characters, Marinette discovers the Peacock Miraculous while on a solo adventure. She has to figure out how to use its powers, which are different from the Ladybug Miraculous she's used to. This could lead to some really interesting character development as she tries to master a new set of abilities.
One possible fanfiction could be about Marinette transforming into a mouse - themed Miraculous holder. Maybe she discovers a new mouse - themed Miraculous in a hidden part of Paris. This could lead to her having new powers like super - speed and the ability to fit into small spaces. She could use these powers to outwit Hawk Moth's akumas in a really unique way, and her relationship with Adrien might also take an interesting turn as she tries to keep her new identity a secret from him.
In Miraculous Ladybug fanfiction, Marinette in a bikini could be part of a beach - themed story. Maybe she's on vacation with her friends. It could be a fun and light - hearted scenario where she shows off her confidence and style while enjoying the sun and sand.
I really like 'The Hidden Bond'. In this fanfiction, Marinette discovers a new side to Cat Noir that she hadn't seen before. It's full of cute moments and some really well - written dialogue. It also has an interesting plot that keeps you hooked from start to finish.
There are many fanfictions where Marinette sings. In some, her singing might be related to her expressing her feelings for Adrien. For example, she could sing a song she wrote herself about her secret love for him. It adds a creative and emotional aspect to the story.