Obviously, Naruto is the central character as the one whose gender is changed. Sasuke is often a part of the harem, his brooding nature adding an interesting dynamic. Sakura might also be included, but in a different role, perhaps as a friend or a rival to the female Naruto. Kakashi could also show up, being a mentor figure who has to deal with this new situation.
Definitely Sasuke. He has a complex relationship with Naruto, and in a gender - bender situation, that relationship could take on a whole new romantic dimension. Sakura could also be in the harem. She has always had strong feelings for Sasuke, but with Naruto's new form, she might develop different feelings. And then there's Hinata, who has always been in love with Naruto, and this gender - bender concept could add more depth to her feelings.
One interesting plot could be that Naruto is turned into a female and suddenly finds herself in the middle of a harem of his former male friends who are now attracted to her in this new form. They all compete for her attention in different ways, like Sasuke showing his softer side more often to win her over.
Definitely Naruto himself (as the gender - bended version). Since the whole concept often revolves around him changing genders, he's at the center of most of these fanfictions. Another popular character would be Sasuke. His relationship with a gender - bended Naruto always makes for an interesting dynamic.
One common theme is the exploration of different relationships. For instance, how Naruto's friendships with characters like Sakura and Kakashi change when his gender is different. Another theme is the challenge of fitting into the ninja world. As a gender - bent Naruto, the character might face different expectations and prejudices. For example, if Naruto is female, she may have to deal with sexism in the male - dominated ninja society.
One common theme is the exploration of changed relationships. Since Sasuke is female, the dynamic between Naruto and her is different. It could be more of a romantic tension in some fanfictions.
One common theme is self - discovery. When the character's gender is changed and they travel back in time, they often have to re - evaluate who they are. For example, a male - turned - female Naruto might discover new aspects of themselves in the different time period. Another theme is changing the past. They try to fix things that went wrong in the original Naruto timeline. And relationship dynamics also change. New friendships and romances can form due to the gender - bender and time - travel elements.
One common theme is the exploration of relationships. For example, if Naruto is a girl, how would her relationship with Sasuke change? It could become more of a romantic relationship earlier or have different dynamics. Another theme is the struggle against gender stereotypes. A female Naruto might face different expectations from the village and have to fight harder to be taken seriously as a ninja. Also, the theme of self - discovery is often present. The gender - bent characters have to re - evaluate who they are in this new gender - swapped world.
One idea could be that Naruto is turned into a girl by a strange jutsu accident. The members of his harem could include Sasuke, who is now intrigued by this new Naruto, and Sakura, who becomes more protective. Another could be that Naruto enters a new dimension where gender roles are reversed for everyone, and he has to navigate this new world while building his harem.
Probably Female Thor. She brings a new and exciting take on the character. Her story can be different from the male Thor's, like how she might handle her relationships with other Asgardians or mortals. Another popular one could be Male Black Widow. People are often interested in seeing how a male version of this complex and deadly assassin would operate. And also Female Iron Man. The idea of a woman in the role of Tony Stark, with her own unique style and approach to technology and heroism, is really appealing.
Natsu is quite popular. Since he's one of the main characters, seeing him as a female brings a whole new dimension to his relationships and his fiery personality. People like to imagine how his interactions with Happy and the rest of the guild would be different.