Well, it's Naruto and Ino. Naruto, with his orange jumpsuit and his dream of becoming Hokage, is now in a very different physical form. Ino, who is part of the Yamanaka clan, has to deal with Naruto's different physical capabilities and social standing. They are the two central characters around which all the body - swap chaos and story development revolves.
The main characters are Naruto and Ino. Naruto, the underdog turned hero, has to navigate Ino's life, her relationships with her friends like Sakura and Shikamaru. Ino, on the other hand, has to handle Naruto's reputation, his relationships with Kakashi - sensei and the rest of the gang, and of course, his unique ninja skills.
The main characters are Naruto and Ino, obviously. Since it's a body - swap fanfiction about them, they are the central focus. They are the ones who will experience the strange situation of being in each other's bodies and will have to deal with all the consequences.
Well, usually in such body - swap fanfics, there could be a lot of interesting plots. For example, Naruto and Ino would have to adjust to living in each other's bodies. Naruto might struggle with Ino's more delicate and feminine ways, while Ino could find Naruto's rough - and - tumble ninja life a real shock. They might also have to keep their body - swap a secret from others, which could lead to some really comical and tense situations as they try not to blow their cover.
Another plot could be that the body swap was caused by a strange jutsu gone wrong. In the process of trying to fix it, they end up learning more about each other. Naruto could understand Ino's insecurities better, and Ino could see Naruto's determination and the weight of his responsibilities more clearly. This new - found understanding could change their relationship for the better even after they swap back.
One common theme is self - discovery. When the characters swap bodies, they often learn new things about themselves. For example, they might realize how others perceive them.
The key is in the dialogue and small actions. For example, if Finn and Jake swap bodies, Finn (in Jake's body) could still show his brave and adventurous spirit through the way he approaches challenges, even if he has to do it in Jake's form. He can say things like 'Jake, I mean, me - Finn - in - Jake's - body, is still gonna go out there and fight that monster!'. Jake (in Finn's body) could maintain his laid - back nature by lounging around in Finn's clothes but still giving Finn - like advice in his own Jake - ish way. The characters should also react to the new body's abilities or limitations in a way that reflects their original personalities. If Princess Bubblegum and Marceline swap, Princess Bubblegum (in Marceline's body) might be disgusted by the idea of drinking blood but still be very methodical in trying to find a way around it, which is very much like her scientific and organized self.
Comedy is also a big theme. Just imagine Naruto trying to do Sasuke's brooding look while in his body, or Sasuke being forced to eat Naruto's favorite ramen. It's all about the humorous situations that come from the characters being in the wrong bodies.
One great 'Team 7 Body Swap Naruto Fanfic' is 'Swapped Fates' on FanFiction.net. It has an interesting take on how Naruto, Sasuke, and Sakura handle being in each other's bodies. The author does a good job of exploring their personalities in these new situations.
One common theme is identity. When Naruto and Kyuubi swap bodies, they both have to re - evaluate who they are. Naruto has to understand what it means to be a powerful being like the Kyuubi, and the Kyuubi has to come to terms with being in a human form.
Ben Tennyson would definitely be one of the main characters as he is the central figure in the Ben 10 series. Gwen, his cousin, could also be involved as she is often by his side in the original series. Kevin Levin might also be part of it, especially if the story involves a more complex web of body swaps and relationships among the main characters.
Obviously, Naruto and Ino would be main characters. Their parents, like Minato and Kushina for Naruto, and Inoichi for Ino, could also play important roles. Maybe even their grandparents if there are any backstories to explore.