In a fanfiction where Luffy turns into a girl, the story could take an interesting turn. Luffy's dreams of becoming the Pirate King wouldn't change, but the way he approaches it might. As a girl, he could use his charm to get out of some tricky situations. For example, when dealing with some of the more traditional pirates or marines who might underestimate a girl. Also, the Straw Hat crew's dynamic would shift. Zoro might be more protective, not that he isn't already, but in a different way. And Chopper would be super curious about the sudden change and would constantly be checking if there are any medical reasons for it, even though it's a magical fanfiction change.
His core personality might not change much. Luffy is still likely to be as carefree and adventurous as ever. However, he might become a bit more sensitive to certain things, like how people treat girls. He'd still be fearless in the face of danger, but could use his new form to his advantage in different ways, like when dealing with female characters who might be more likely to trust a girl.
One popular theme is adventure. Just like in the original One Piece, fanfiction might focus on Luffy and the girl character going on new and exciting adventures, exploring uncharted islands and facing powerful enemies. Another theme could be friendship. They could form a special bond that helps them overcome difficulties. And of course, there's the theme of self - discovery. The girl might learn more about herself while traveling with Luffy and his crew.
One possible idea for a fanfic where Luffy is a girl could be that she has a different approach to leadership. Instead of the brash and straightforward style, she might use her charm and a more empathetic side to bring the crew together. For example, she could be more in tune with the emotional needs of her crewmates like Nami and Robin, and this could lead to deeper and more meaningful relationships within the crew.
The Marines could still be antagonists. They might view Luffy's transformation as a sign of weakness or an opportunity to capture her more easily. They could underestimate her because she is now a girl, but of course, they would be wrong.
Nami is quite memorable. In fanfiction, she could have new interactions with Luffy in a girl - centered story. Her intelligence and her ability to navigate are assets. Another is Robin. Her mysterious past and her calm demeanor make her interesting in the context of fanfiction with Luffy. She might share some deep secrets or knowledge with Luffy in these stories.
One popular type of 'One Piece' fanfiction involving Luffy and Dragon might be about their eventual reunion. Since Dragon is Luffy's father, many fans like to imagine the moment when they meet again. In some fanfictions, Dragon could be secretly guiding Luffy's journey without him knowing. This adds an interesting layer of mystery to Luffy's adventures as he is unknowingly following a path his father has some influence over.
One possible fanfiction could be about Zoro and Luffy's unwavering loyalty to each other. Zoro is always there to protect Luffy and vice versa. They might face a powerful enemy that tests their bond, and through their combined strength and trust, they emerge victorious.
If Luffy was kidnapped in a fanfiction, his crew would surely go to great lengths to rescue him. Nami would probably come up with a smart plan, using her knowledge of the seas and navigation. Zoro would be ready for a fight, not fearing any opponents in the way. Sanji would keep everyone fed during the rescue mission, while also being prepared to kick some kidnapper butts with his powerful kicks.
Perhaps there could be a plot where Luffy, as a girl, has to use different strategies in battles. Since the opponents might underestimate a female opponent, Luffy could use this to her advantage and surprise them with her strength. This would also show a different side of Luffy's combat intelligence.