Team Rocket, of course. Jessie, James, and Meowth would see Ash as Ashley and might come up with new schemes to catch Pikachu. They could be completely thrown off by Ash's new appearance and behavior. Professor Oak could also play a role. He might be the one to figure out how to turn Ash back to his original form or provide some scientific explanations for the transformation. Another potential character could be Dawn. She could meet Ashley and be inspired by her unique approach to Pokemon training, which was originally Ash's but has a different flavor in Ashley's form.
Potential characters might include a new group of Pokémon thieves that Ash has to deal with. Also, there could be a local Pokémon healer who becomes an important part of the story. There might be some young Pokémon enthusiasts who look up to Ash and join him on his adventures. Another possibility is a reclusive Pokémon trainer who has some rare Pokémon and Ash tries to learn from them.
The main characters are Ash and Ashley. Ash is our familiar hero with his Pikachu by his side, always eager to catch more Pokemon and become a Pokemon Master. Ashley, on the other hand, can be anything from a fellow trainer who has a special connection with Ash, to a character with a mysterious past related to the Pokemon world. In some fanfics, she might have a rare Pokemon or a special ability that draws Ash to her and they embark on adventures together.
Ash is often seen as the more action - oriented of the two. He could be the one who has special skills like combat or magic in some fanfictions. Ashley, though, has her own charm. She may be good at making friends, which helps them in their adventures. Their relationship can range from being just friends to having romantic undertones, depending on the direction the fanfiction author takes.
Well, it could be that the fanfic focuses on a parallel universe where Ash is magically turned into Ashley. This could lead to different storylines. Maybe Ashley (formerly Ash) has to deal with the different expectations that come with being a female in the Pokemon world. She might face new challenges in terms of how she is perceived by other trainers, and also how she interacts with female - only Pokemon groups or events.
Obviously, Ash's main friends like Misty and Brock would be involved. Misty could be the one who first notices Ash's strange new ability and helps him keep it a secret at first. Brock, with his knowledge of Pokemon, could try to figure out how to reverse the shapeshifting if it becomes a problem. Also, Team Rocket would be great characters in this. They could constantly be trying to capture Ash in his different shapes, thinking they've discovered a new and valuable Pokemon.
I think Gary would be a great addition. His rivalry with Ash could create some interesting storylines. He might start off as a bit of a antagonist but then end up being an ally. Also, Dawn could be included. She has her own unique style of training Pokemon and her friendship with Ash could be further explored in the context of Ashley being there as well. And then there's May, who could bring in her Contest experiences and help Ash and Ashley in different ways related to Pokemon showcases.
A frequent theme in such fanfiction could be adventure. Even as Ashley, the character would still be involved in Pokemon - related adventures. But now, with a different gender, there could be new challenges and opportunities. For example, interactions with other characters, especially of the opposite gender, might change. Also, the theme of self - discovery is quite common. Ashley would need to figure out who she is in this new form and how she fits into the Pokemon world.
Well, Pikachu would still be a main character. Since Ash, now as a girl, has Pikachu as her partner Pokemon, Pikachu would be right there with her on her adventures. Also, Misty could have a different dynamic with Ash as a girl. Maybe they become closer friends or even rivals in a new way.
There could be Cilan, Iris, and the Gym Leaders in Unova. They might cross paths with Ash and Misty during their adventures.
You can try looking on some well - known fanfiction websites like FanFiction.net or Archive of Our Own (AO3). They usually have a wide range of Pokemon fanfictions, and there's a good chance you'll find 'pokemon ash tg to ashley' ones there.