In 'Gary turns Ash into a girl' fanfiction, there could be themes related to power dynamics. Maybe in this new form, Ash has different abilities or is treated differently in battles or competitions. The theme of adaptation is also likely. Ash has to adapt to a new physical form and the social implications that come with it. Additionally, there could be a theme of mystery, like how and why Gary was able to turn Ash into a girl, and what are the consequences of this transformation in the long run.
One possible theme could be identity. Ash, now as a girl, would have to re - evaluate who he/she is. Another theme might be relationships. His/her relationships with Gary and other characters would likely change in interesting ways.
I'm not sure of specific 'Gary turns Ash into a girl' fanfictions. You can try searching on fanfiction - specific websites like FanFiction.net or Archive of Our Own. Just use those keywords in their search bars and you might find some interesting works.
One possible theme is the transformation of a rivalry into something deeper. Gary and Ash were rivals, but in this fanfiction, it could be about how that rivalry can turn into love or a very strong friendship. Another theme might be self - discovery. Gary might be on a journey of realizing his true feelings for Ash.
One possible plotline could be that Ash, as a girl, might face more discrimination in the male - dominated Pokemon trainer world at first. But she overcomes this with her determination and unique skills, proving that gender doesn't matter in Pokemon training.
One possible plotline could be that it's set in an alternate universe where some magic or strange phenomenon causes them to become pregnant. Another could be a scientific experiment gone wrong scenario. But these are just wild speculations as such a concept is very far - fetched from the original Pokemon concept.
Rivalry - turned - friendship is a big one. They start as rivals competing for the same goals, but then realize they can support each other. Also, adventure themes are common. They go on Pokémon - catching adventures together, facing challenges like powerful wild Pokémon or evil organizations. It's about them learning to work together in these situations.
In Ash and Gary Alola fanfiction, the theme of self - discovery is also common. Both characters may learn more about themselves while in Alola. Also, the theme of competition still exists, but it's more about friendly competition to improve themselves rather than just winning. For example, they might compete in a local Alola Pokemon battle tournament. They also might learn about the importance of teamwork when dealing with the new and powerful Alola Pokemon.
One popular theme is their rivalry. How they constantly try to outdo each other in Pokémon battles and in their quest to become Pokémon Masters. Another is their growth as trainers, and how they influence each other's development.
It could be due to a curse. Maybe someone with malicious intent put a curse on Ash that turned him into a girl.
In fanfiction where Ash turns into a girl, it could lead to some interesting plot twists. Maybe his relationships with his Pokémon would change in unique ways. For example, some Pokémon might be more protective of him now that he's a girl. Also, his interactions with other trainers, like Misty and Brock, would be different. They might treat him with more chivalry or have different emotional responses to his new form.
A third possible storyline is that they get lost in an unknown region. They would have to rely on each other's skills and the abilities of their Pokemon to find their way out. Along the way, they could learn more about each other and form new friendships or rivalries. Ash might be more impulsive in trying to find a way out, while Gary could use his knowledge to analyze the situation. Red and Green might have some old - fashioned wisdom to contribute as well.