Well, Ash joining Team Skull in a fanfiction could lead to some interesting character interactions. He could befriend Guzma and they could exchange their views on Pokémon battles. Ash might also try to reform the more unruly aspects of Team Skull, making them more like a proper Pokémon training group.
One possibility is that Ash brings his unique battle skills to Team Skull. He might start teaching the members new strategies, which could change the whole dynamic of the team. For example, his bond with his Pokémon could inspire the Team Skull members to form stronger relationships with their own Pokémon.
Another thing that could occur is that Ash's friends would be very suspicious. They might think Ash has gone to the dark side. So they could try to rescue him. This would lead to a lot of drama and action. There could be epic battles between Ash's friends and Team Flare while Ash is caught in the middle, trying to figure out what to do and where his loyalties truly lie.
Well, in such a fanfiction, Ash might start using Team Rocket's sneaky tactics. He could learn from them how to be more devious in catching Pokémon. For example, he might use their elaborate traps instead of his usual straightforward battles. This would be a huge change from his normal good - guy image.
Well, if Ash joined Team Rocket, he'd probably bring a whole new dynamic. His skills as a trainer could be used in unexpected ways. Maybe he'd try to reform Team Rocket from the inside, using his kind heart and love for Pokémon to change their ways. He could also introduce new strategies for capturing Pokémon that are more ethical than Team Rocket's usual methods.
Ash joining Team Galactic in fanfiction could mean a complete shift in his character arc. He might be forced to do things against his will at first. But as time goes on, he could use his knowledge of Pokemon to gain an upper hand within the team. For example, he could use his bond with his Pokemon to resist the team's orders that are harmful to Pokemon.
Another possibility is that Serena discovers a secret within Team Flare that could change the whole dynamic of the Pokemon world. It could be a powerful weapon or a hidden plan that is far more dangerous than anyone thought. She then has to decide whether to use this information to her advantage within the team or to try and get it out to the people who can stop Team Flare. This would put her in a very difficult position as she's already in deep with the team.
Well, if Serena joins Team Rocket in a fanfiction, she might bring a new dynamic. Maybe she's forced to join at first. She could use her skills in battles and her knowledge of Pokemon to help Team Rocket in their schemes, but secretly she could be planning to take them down from the inside.
Ash joining Team Rocket could lead to some interesting character dynamics. He might start to question his own values. For instance, he's always been about friendship with Pokemon, but Team Rocket is more about using them for gain. This internal conflict could be a major part of the fanfic. Also, his relationship with Jessie, James, and Meowth would change drastically.
Well, in the 'Ash and Misty joins Team Rocket fanfic', they could be brainwashed by Team Rocket's technology or some devious plan. Once they join, they might be given new uniforms and tasks. They could be involved in stealing Pikachu again, but this time from the other side. It would create a whole new dynamic in the Pokémon world, with their old allies now becoming their enemies.
Well, he could be used as a bargaining chip. Team Flare might try to exchange Ash for some powerful Pokémon or valuable items. They could also try to force Ash to reveal any secrets he has about powerful Pokémon or rare items he's come across during his travels.
In a fanfiction where Naruto joins Team 8, he might bring his unique energy and determination. His Rasengan technique could be a great addition to the team's combat capabilities. Also, his friendship with Shikamaru from his original team could influence how he interacts with Shino in Team 8, leading to some interesting dynamics.