Another plot could be that the body swap was caused by a powerful and mischievous Pokemon. As Ash and May are in each other's bodies, they start to understand each other's dreams and struggles better. Ash realizes how hard it is for May to constantly be in the spotlight during Contests, and May understands the pressure Ash feels to be a great Pokemon Trainer.
One interesting plot could be that Ash, now in May's body, tries to enter a Pokemon Contest. He has to quickly learn the skills and grace that May has, like how to style the Pokemon in a more appealing way for the judges. Meanwhile, May in Ash's body decides to enter a Gym battle. She struggles with Ash's more straightforward and battle - focused approach compared to her Contest strategies.
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.
Pikachu might be very confused at first. When it sees 'Ash' (really May in Ash's body) acting differently, it could be hesitant to follow commands as usual. For May's Pokemon, they might be surprised to see 'May' (Ash in May's body) suddenly having a more battle - oriented attitude. For example, May's Beautifly might be confused when 'May' wants to train it for battles instead of focusing on its appearance for Contests.
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.
An interesting plot could involve a strange Pokemon ability that causes the body swap. As they are in each other's bodies, they are forced to travel together to find a way to reverse it. Along the way, they encounter other trainers who notice the strange behavior and they have to come up with excuses. This leads to all sorts of adventures and misunderstandings as they explore each other's lives in a whole new way.
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.
One interesting plot point could be how they adjust to each other's abilities. For example, Ash suddenly having to deal with May's knowledge of Pokémon contests, and May having to handle Ash's battling skills. Another could be the reactions of their friends and Pokémon. Their Pokémon might be confused by the sudden change in their trainers' behavior.
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 interesting plot could be Superman swapping bodies with a normal human. The human then has to deal with Superman's powers while Superman experiences what it's like to be an ordinary person. He might struggle with things like paying bills or getting to work on time in the human's body.
One interesting plot could be Ash forming a unique bond with each Pokémon in his harem. For example, he might have special training sessions with different Pokémon that are tailored to their individual strengths and weaknesses.
One interesting plot development could be the way they adapt to each other's daily routines. Ash in Misty's body might struggle with handling her water - type Pokémon in a more delicate way, while Misty in Ash's body has to deal with his more energetic and sometimes reckless approach to battles. It could also lead to some comical misunderstandings with their friends, like Brock not realizing at first that they've swapped bodies.