One idea could be that Ash, in Serena's body, has to participate in a Pokemon Contest. He would struggle with the grace and style required, but his battle instincts might add an interesting twist. For example, he could use his battle strategies to make his Pokemon's performance more unique. Another plot could be Serena, in Ash's body, trying to enter a Pokemon League. She might face challenges in understanding the more rough - and - tumble nature of battling compared to contests. Also, they could both have to deal with how their friends react to their changed personalities in the wrong bodies.
If Ash was in Serena's body, his relationship with her friends like Bonnie and Clemont would change. Bonnie might be a bit confused as Ash's more boyish and impulsive nature shows through Serena's body. Clemont might be surprised at some of the battle - like decisions Ash makes when dealing with things like helping around the lab. On the other side, if Serena was in Ash's body, her relationship with Ash's rivals like Gary would be different. Gary might be intrigued by the more refined and composed 'Ash' he now sees.
Adaptation is also a big theme. Ash has to quickly adapt to the new body's abilities, limitations, and sometimes even different personalities. This can range from getting used to a new physical form in a body swap with a Pokémon, to dealing with the different skill sets of another trainer in a human - human body swap. It's all about how he copes and thrives in the new situation.
Another theme is relationship exploration. This body swap situation can bring out different dynamics in their relationship. For example, they might understand each other's feelings better. Also, there could be a lot of humorous situations as they try to navigate the world in each other's bodies. They may struggle with things like how the other behaves in certain situations or how to interact with their Pokémon in a different body.
Another theme is adaptation. Ash has to quickly adapt to the new body's physical abilities, like different levels of strength or agility. This often leads to some really interesting scenarios where he has to figure out how to battle or move around in a completely different way. For example, if he swaps with a smaller trainer, he might have to find new strategies for catching Pokemon. Also, there's often the theme of friendship. His friends might not recognize him at first, and he has to prove that he's still Ash on the inside, which shows the strong bonds of friendship in the Pokemon world.
Perhaps a major plot twist could be that the body swap is not accidental but part of a bigger plan by a mysterious villain. This villain could be using their body swap to gain access to something that only Ash or Iris can reach in their normal bodies. For example, there could be a special Pokémon or a powerful item. And as they try to figure out how to swap back, they also have to deal with this new threat, which adds a whole new layer of complexity to the fanfiction.
Yes, there are quite a few. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. Some stories might focus on how Ash and Nurse Joy deal with the swapped bodies, like trying to carry out each other's daily tasks in a humorous way.
One popular place to find 'ash and may body swap fanfiction' could be Archive of Our Own (AO3). There are likely many stories there that explore this interesting concept. You can search for the relevant tags like 'Ash Ketchum', 'May', and 'body swap' to narrow down the results.
One popular 'ash body swap fanfiction' is 'Swapped Worlds' which has an interesting take on the body swap concept involving Ash. It plays with different Pokémon interactions in the swapped state.
One interesting plot could be that Ash, now in Bonnie's body, has to deal with the different social interactions that Bonnie usually has. For example, he might struggle to interact with Bonnie's friends in the way she does. Another plot could be Bonnie, in Ash's body, trying to handle Ash's Pokémon battles. She might use different strategies that surprise everyone. And a third plot could be them trying to find a way to swap back while also learning more about each other's lives.