Jessie and James from Team Rocket are also very popular. Their bumbling yet endearing personalities add a lot of humor to the fanfictions. They are constantly coming up with schemes to catch Pikachu, and their interactions with each other and with Ash's group make for great reading.
Ash is obviously one of the most popular characters. He's the main character of the Pokemon anime, and in fanfictions, his adventures with or against Team Rocket are always interesting. People like to see how he reacts to different situations that Team Rocket creates or how he manages to outwit them.
Obviously, Ash and Jessie, James, and Meowth from Team Rocket are the most popular. Ash is the main hero, and the Team Rocket trio is always causing trouble for him, so they are central to most fanfictions in this theme.
Jesse and James from Team Rocket are always interesting. Their use of hypnosis adds a new layer to their already complex characters. They become more menacing when they can hypnotize their opponents. Also, Ash can be an interesting character in this context. His determination to break free from hypnosis or protect his Pokemon from it shows his strong will. And Pikachu too. Imagine Pikachu trying to fight off the effects of hypnosis while still being its cute and powerful self.
If Team Rocket turns Ash into a Pokemon, it could lead to a really interesting story. Ash would have to experience the world from a Pokemon's perspective. He'd understand their struggles, like being caught and trained. This could also be a way for him to better understand his own Pokemon and their bond with him. And it would be a wild adventure as he tries to find a way to turn back to his human form.
In a fanfiction where Ash joins Team Rocket, it could lead to some really interesting storylines. Ash has a lot of knowledge about Pokémon training that Team Rocket lacks. He could potentially teach them new techniques, but at the same time, his moral compass would be constantly at odds with their devious ways. Maybe he joins them because he's somehow tricked or he has his own secret plan to take them down from the inside. It would be a great opportunity to explore different aspects of his character and how he adapts to this new situation.
Definitely Ash. His journey and how it's affected by the transformation can be the heart of the story. Team Rocket has so much potential. They could be the cause of the transformation, or they could be accidental victims too. Another character worth focusing on is Tracey. He's not as well - known as some of the others, but that could be used to an advantage. He could be the one who discovers a hidden aspect of the transformation. And don't forget about the Pokémon in the Pokémon Center. They could be witnesses to strange happenings related to Ash's transformation and could play a small but important role in the overall fanfiction.
Arceus is quite popular. Given that it's considered the creator of the Pokemon universe in the official lore, it often has a significant role in fanfictions. Mewtwo is also very common. Its powerful psychic abilities and complex backstory make it a favorite for fanfic writers to explore. Another popular one is Lugia. With its majestic appearance and its connection to the sea, it's often a central figure in many stories.
Maxie from Team Magma is often a popular choice. His strong leadership and his extreme beliefs about expanding the land for Pokemon make him an interesting character to explore. Writers can delve into his motives and what led him to such radical ideas.
If Team Rocket turns Ash into a Pokemon, his relationship with his old Pokemon would change. His Pokemon might not recognize him at first. But as they sense his familiar spirit, they could try to protect him. And Ash, in his new form, could learn a lot about the true nature of Pokemon. He could discover secrets about their evolution, abilities, and the hidden powers within them that he never knew as a human trainer.
One thing that would happen is that his Pokémon battles would take on a whole new meaning. Instead of battling for the sake of becoming a Pokémon master, he might be battling to further Team Rocket's goals. His Pokémon would have to adjust to this new purpose. Also, Ash would probably have to wear Team Rocket's uniform, which would be a really strange sight for fans who are used to seeing him in his normal get - up.
One interesting storyline could be Team Rocket actually helping Ash in a dire situation. Maybe they realize that a greater evil is about to destroy the Pokemon world and they decide to team up with Ash for once. Their skills in stealing and sneaking around could be useful in gathering information about this new threat.