Ash could also become more distrustful. Team Rocket is known for their tricks and lies. After spending time with them, Ash might start to question the motives of others more often. He might not be as quick to trust new people or Pokemon he meets on his journey.
On the other hand, he could develop a sense of sympathy for Team Rocket members. If he gets to know them on a deeper level, he might understand why they do what they do. This could make him more empathetic and less quick to judge, which is a big change from his usual somewhat black - and - white view of good and bad in the Pokemon world.
He might become more cautious. Usually, Ash is quite bold and rushes into things. But if he's in a Team Rocket - centered fanfiction, he'd likely be more careful as he's constantly surrounded by danger. For example, he'd think twice before challenging a new Pokemon or entering an unknown area.
Pikachu would probably be very confused at first. It's used to fighting against Team Rocket, not being on their side. It might resist and try to zap Ash to snap him out of it.
One thing that would happen is that his Pokémon battles would take on a whole new meaning. Instead of battling for the sake of becoming a Pokémon master, he might be battling to further Team Rocket's goals. His Pokémon would have to adjust to this new purpose. Also, Ash would probably have to wear Team Rocket's uniform, which would be a really strange sight for fans who are used to seeing him in his normal get - up.
In a fanfiction where Ash joins Team Rocket, it could lead to some really interesting storylines. Ash has a lot of knowledge about Pokémon training that Team Rocket lacks. He could potentially teach them new techniques, but at the same time, his moral compass would be constantly at odds with their devious ways. Maybe he joins them because he's somehow tricked or he has his own secret plan to take them down from the inside. It would be a great opportunity to explore different aspects of his character and how he adapts to this new situation.
Well, Ash is known for his adventurous and curious nature. In Mewtwo's body, that adventurous spirit might be redirected. Instead of running around exploring physically, he might use Mewtwo's psychic powers to explore the minds of other Pokemon or discover hidden places in the psychic realm. His personality would also become more complex as he'd have to deal with Mewtwo's memories and emotions. He'd still be the same Ash at heart, but there would be an added layer of depth and thoughtfulness, perhaps a bit of melancholy too as he'd understand Mewtwo's pain of being created for the wrong reasons. And his interactions with other Pokemon and humans would be different. He might seem more intimidating at first because of Mewtwo's appearance, but as soon as he started to communicate, his friendly and helpful Ash - like personality would show through.
In Paldea, the interactions could change because of the different cultures and Pokemon battles. For example, if there are new battle styles in Paldea, Ash would be eager to learn and participate. Team Rocket might try to disrupt these battles to steal Pokemon. But as they interact more, they could start to understand each other better. Ash could see that Team Rocket might be more desperate for success in this new region, and Team Rocket could see Ash's determination to adapt and grow.
Some of his more loyal Pokemon might try to resist the change. For example, Pikachu could use electric shocks to try and jolt Ash back to his senses. Pikachu has a strong bond with Ash and would be very confused and sad about his decision to join Team Rocket.
Well, Ash's Pokémon are a diverse bunch. His Heracross could use its Horn Attack to directly combat Team Rocket's Pokémon. Totodile could use its playful nature to confuse Team Rocket's Pokémon. And Ash's Bayleef could use its Razor Leaf to cut through any ropes or barriers that Team Rocket has set up to restrain Dawn. All of his Pokémon, with their unique abilities, would work together under Ash's command to save Dawn from Team Rocket.
If Ash were to turn into a Pokemon in a fanfic, his personality would surely be affected. He's used to being in control as a trainer, but as a Pokemon, he'd have to learn to follow others' commands or work within a group. His once outgoing and friendly nature might become more cautious. He'd have to be more aware of predators and threats. And his competitive spirit might take on a different form. Instead of competing in trainer battles, he'd be competing in Pokemon - on - Pokemon battles, which could make him more aggressive or strategic depending on the Pokemon he turns into.
One interesting storyline could be Team Rocket actually helping Ash in a dire situation. Maybe they realize that a greater evil is about to destroy the Pokemon world and they decide to team up with Ash for once. Their skills in stealing and sneaking around could be useful in gathering information about this new threat.
One idea could be that Ash feels betrayed by his friends because they always overshadow his achievements. So, in a fit of anger and disappointment, he decides to join Team Rocket. He might think that with their resources, he can finally become a more powerful trainer on his own terms.