Let's start with the Avengers. In Spider - Man's body, Jane would interact with the Avengers in a unique way. She would bring her scientific knowledge to the table, which could be very useful in some situations. However, her different personality might cause some friction. For example, Iron Man might be intrigued by the new 'Peter' but also a bit annoyed at the different approach. Captain America might see the change in 'Peter' as a sign of him growing up in a different way. On the other side, Spider - Man in Jane's body would have to deal with Asgardian friends and foes. He would befriend some of the more adventurous Asgardians, but also face the jealousy of some who don't like this 'outsider' in Jane's body. Overall, their body swap would create a lot of chaos and interesting changes in their relationships with other characters.
Their relationships would change significantly. For instance, their friends might be very confused at first. Spider - Man's friends would see the Wasp acting differently in his body, and vice versa. Their romantic relationships, if any, would also be affected. They would have to explain the situation to their loved ones, and it could lead to some awkward or comical moments.
If Naruto is in Sakura's body, his relationship with Sasuke might change. Sasuke might be initially confused by the 'new' Sakura's more Naruto - like behavior. Naruto might also have a different perspective on how Sakura views Sasuke. For Sakura in Naruto's body, her relationship with Kakashi could be different. Kakashi might notice the change in 'Naruto' and be more cautious. Also, Naruto's friends like Shikamaru might be puzzled by the sudden shift in 'Sakura's' personality.
If Ash was in Serena's body, his relationship with her friends like Bonnie and Clemont would change. Bonnie might be a bit confused as Ash's more boyish and impulsive nature shows through Serena's body. Clemont might be surprised at some of the battle - like decisions Ash makes when dealing with things like helping around the lab. On the other side, if Serena was in Ash's body, her relationship with Ash's rivals like Gary would be different. Gary might be intrigued by the more refined and composed 'Ash' he now sees.
Peter's colleagues at the Daily Bugle would find it very strange. J. Jonah Jameson would probably think it's some sort of elaborate prank by Spider - Man. He might try to expose this 'new Spider - Man' who is actually Mary Jane in his body. Mary Jane's family and friends would also be concerned about her well - being. They would try to communicate with her, but it would be difficult because she's in a different body. And Spider - Man's other friends in the superhero community might initially suspect that he's been mind - controlled or something similar, which would lead to a lot of drama and attempts to 'fix' him.
One interesting plot twist could be that while in Spider - Man's body, Jane discovers a new side of Peter Parker's life. She realizes the daily struggles he has in balancing his superhero duties and personal life. Maybe she accidentally reveals Spider - Man's identity to some of his enemies while trying to handle a situation in a different way than Peter would. This could lead to a whole new set of challenges for both of them as they try to fix the mess and get their bodies back.
If Batman is in Wonder Woman's body, his relationship with Aquaman could change. Aquaman is used to dealing with Wonder Woman in a certain way, but now he'd sense a different approach. Batman would also have to navigate Wonder Woman's relationship with the gods. This could be a huge challenge for him as he doesn't have the same connection to the divine. When Wonder Woman is in Batman's body, she would change how Batman is perceived by Commissioner Gordon. Gordon might find this new 'Batman' more approachable and less brooding. And she would likely have a different way of dealing with the rogues gallery in Arkham Asylum.
If Anakin and Obi - Wan swapped bodies, their master - apprentice relationship would be turned upside down. Obi - Wan in Anakin's body would have to deal with Anakin's more impulsive nature and his connection to Padmé. Anakin in Obi - Wan's body would have to take on the role of the more level - headed mentor, which would be a huge adjustment for him. Their interactions with other Jedi and in battles would be very different as they struggle to adapt to each other's personalities and abilities.
One interesting plot twist could be that while in each other's bodies, they have to deal with their respective personal relationships. Mary Jane in Spider - Man's body might struggle to handle his superhero duties and his complex relationships with villains. Meanwhile, Spider - Man in Mary Jane's body has to deal with her acting career and the pressures that come with it. Another plot twist could be that they start to understand each other on a much deeper level. Spider - Man realizes how difficult it is for Mary Jane to be constantly in the public eye and worried about his safety, and Mary Jane gains a newfound respect for the challenges he faces as a superhero.
His relationship with Aunt May would likely become more strained as she becomes overprotective, fearing she could lose him too. With his friends at school, he might become more distant as he is preoccupied with superhero duties. He could also be more cautious around MJ, not wanting to put her in danger in the new, more dangerous world.
In a reverse Spider - Man story, the relationship with the police could be reversed too. Normally, Spider - Man has an uneasy but mostly positive relationship with the cops. But if Peter is causing trouble, the police would be actively trying to catch him. Also, his relationship with other superheroes in the Marvel universe, if they exist in this story, would be completely different. They would likely view him as a threat and try to stop him rather than collaborate with him as they might in the traditional story.