One possible plotline could be Bonnie becoming overly possessive of a particular Pokemon. For example, she might not let anyone else interact with it. Another could be her having a yandere - like obsession with a trainer, following them around everywhere in the Pokemon world.
Obviously Bonnie is a main character. And often, there will be a Pokemon that she has an obsession with. It could be a popular one like Pikachu or Eevee. There might also be a trainer who becomes the target of her yandere behavior.
In the fanfiction, Bonnie's Pokemon might develop new abilities or behaviors due to the mermaid influence. Her Sylveon could start to communicate with the mermaids in a unique way, perhaps using its ribbons to send messages. This would make Bonnie see her Pokemon in a new light, and their relationship would grow deeper as they all adapt to this new situation together.
There's a fanfiction called 'Bonnie and the Mysterious Eevee'. In this one, Bonnie stumbles upon an Eevee with unusual powers. It's a really heartwarming story as she tries to understand and help the Eevee. It shows Bonnie's kind heart and her determination to do what's right for Pokemon.
One common theme is obsession. Cynthia's yandere nature often leads to her being overly obsessed with another character, usually the protagonist. Another theme is possessiveness. She will go to great lengths to keep the person she's fixated on all to herself. And there's often a sense of danger as her extreme behavior can put others in jeopardy in the Pokemon world.
One possible scenario in fanfiction could be that Bonnie catches a strange illness from a new Pokemon she encounters in the Kalos region. This illness might cause her to lose her energy and enthusiasm, which are her usual traits. Her friends, Clemont and the protagonist, would then search for a cure.
The main characters are Clemont and Bonnie. In fanfiction, they are often depicted in various scenarios. Clemont is known for his glasses and his lab coat, always tinkering with something. Bonnie is cute and spunky, often with her Dedenne by her side. Their interactions with other Pokemon trainers, their Pokemon, and the different environments they explore are what make up the core of the fanfiction stories.
One possible fanfiction could be where Bonnie catches a rare Pokemon - related illness. Maybe she got it from exploring an old, mysterious forest in the Pokemon XY world. Her friends, like Ash and Clemont, would then have to search for a cure. They might visit different Pokemon Centers and ask the Nurse Joys for help, but find that this illness is something they've never seen before.
In 'pokemon max and bonnie fanfiction', a frequent theme is exploration. They might be exploring new regions in the Pokemon world, discovering new Pokemon species. Also, teamwork is quite common. They join forces to battle against strong opponents or solve problems that come their way in the story. Sometimes, there are also themes related to family, like how their families influence their Pokemon - training journey.
Max is also a top character. His knowledge about Pokemon makes him a valuable asset in any story. He could use his smarts to figure out how to defeat a powerful enemy Pokemon or how to solve a mystery related to a certain Pokemon species. In many fanfictions, he is the one who comes up with the plans.