One idea is that Ash enters a hidden tournament where the rules are different. To compete, he has to endure intense physical training, which gradually makes him muscular. Another could be that a powerful Pokemon's aura has an impact on Ash's body, causing him to become more muscular as he spends time with it.
One possible fanfiction could be about Ash training really hard in a special region where he discovers a new type of Pokemon that has a unique energy. This energy somehow affects his physical development, making him muscular. He then uses his newfound strength to overcome tougher challenges in battles.
Ash could be a Pokémon trainer with a different starting point in this fanfiction. Born in 1987, by 1997 he might have already made a name for himself in local Pokémon battles. He could have a team of Pokémon that he rescued from difficult situations, like a Charmander that was abandoned by its trainer. His story could revolve around giving these Pokémon a second chance and proving that Pokémon don't need to be 'perfect' to be strong.
In some fanfictions, the girl's clothes are related to her Pokemon evolution journey. Maybe when her starter Pokemon evolves, she gets a new set of clothes that symbolizes their growth together. It could be a more elaborate and powerful - looking outfit. Also, there are often stories where she dresses up to impress Ash or to show her confidence during a difficult battle. This could involve a flashy, battle - ready costume with bright colors and strong - looking boots.
One interesting idea could be Ash having unique hybrid Pokemon companions. For example, a Pikachu with some other type's features. Another could be Ash himself having some hybrid abilities, like being able to communicate with Pokemon in a new and enhanced way.
One idea could be that Ash discovers a new type of Pokemon that has unique abilities and is the key to solving a big mystery in the Pokemon world. For example, it might be able to communicate with humans in a way no other Pokemon can, and Ash has to learn how to work with it to stop an evil organization from using this Pokemon's power for bad.
One idea could be to explore Ash's first encounter with Pikachu from Pikachu's perspective. Maybe Pikachu was initially scared of Ash but then grew to trust him over time. Another idea is to write about Ash's first gym battle in a more detailed and dramatic way, like adding some internal thoughts of Ash during the battle.
One idea could be a fanfiction where a girl joins Ash on his journey. She might have a unique Pokemon that helps Ash in a difficult battle. For example, she could have a psychic - type Pokemon that can sense the opponents' next moves and help Ash strategize better.
One popular plot idea could be Ash and Anabel teaming up to face a powerful new Pokemon that has been causing chaos in a region. They combine their skills and knowledge to figure out the Pokemon's weakness and ultimately defeat it.
Maybe in the fanfiction, Elesa's Pokemon get lost in an unknown region and Ash offers to help her find them. During their search, they encounter rare and powerful Pokemon, and they also discover a hidden mystery about the region that they are in. This adventure could strengthen their friendship and respect for each other.
A possible plot is that Ash is separated from his friends during a powerful storm. Alone, he stumbles upon an ancient Pokemon ruin. He then has to decipher the secrets within the ruin with the help of his Pokemon, all while trying to reunite with his friends. He might learn some long - forgotten Pokemon training techniques in the process.