Well, if Ash turns into a legendary Pokemon, he'd likely gain a whole new set of powers. For example, if he becomes Arceus, he'd have the power to create and shape the Pokemon world. He could create new Pokemon species or even reshape the existing regions. His friends would probably be both in awe and a bit scared at first. But Ash, being Ash, would still have his kind heart and would use his powers for good.
Suppose Ash turns into Ho - Oh. Ho - Oh is a symbol of hope and resurrection in the Pokemon lore. Ash could bring new life to areas that have been damaged by human or Pokemon conflicts. He could also inspire trainers and Pokemon alike to strive for better things. His Pikachu might have a special bond with him still, and they could work together in new and amazing ways. Ash as Ho - Oh could also travel to different dimensions and bring back knowledge and power to help the Pokemon world.
In fanfiction where Ash turns into a Pokemon, there are numerous possibilities. One is that he could form a deeper bond with other Pokemon. Since he is now one of them, they might trust him more instinctively. He could also be hunted by some trainers who see him as a rare or powerful Pokemon. This would put him in a difficult situation where he has to avoid capture while still trying to live as a Pokemon. And his old friends like Pikachu might have a hard time adjusting to this new Ash - Pokemon hybrid existence.
If Ash becomes a legendary Pokemon in a fanfic, it would change the whole Pokemon world dynamic. He might be hunted by evil organizations who want to use his power. On the other hand, he could also use his new form to protect the Pokemon world better than ever. His friends would likely have a mix of reactions, from being amazed to being worried about losing the old Ash.
Perhaps Ash, as a Victini, would attract a lot of attention from other Pokémon and trainers. Some might see him as a symbol of hope and victory, while others could be jealous or even try to capture him for his powers. His friends, like Pikachu, might be initially confused but would eventually learn to accept this new form of Ash and help him navigate the challenges that come with being a Victini.
Well, he might start to see the world from a Pokemon's perspective. For example, he could understand their communication better and form closer bonds with them. He may also face new challenges like having to adapt to living in a Pokeball or dealing with the natural instincts of his new Pokemon form.
Well, perhaps Ash could gain new and amazing powers. Shiny pokemon often have special abilities or appearances, so if Ash turns into one, he might be able to fly like a shiny bird - type pokemon or have super strength like a shiny fighting - type. He could also use his new form to communicate better with pokemon, since he'd be more like them.
Another possibility is Ash becoming Lugia. Lugia is known as the guardian of the seas. As Lugia, Ash could explore the deep oceans, discover new species of Pokemon, and safeguard the marine ecosystem. He could use his psychic and flying abilities to interact with both water - and flying - type Pokemon, bringing a new era of harmony between different Pokemon types.
In a Pokemon Ash turns evil fanfiction, he might start using his Pokemon for wrong purposes. For example, instead of battling for sport and friendship, he could use them to steal from other trainers or take over Pokemon Centers. His Pikachu, usually so loyal, might be conflicted about following his new, evil ways.
A lot could change. His fashion sense might be completely different. Instead of his usual cap and jacket, he could be wearing more feminine outfits. His Pokémon might need to get used to this new look too. Pikachu might be a bit confused at first but then adapt. Also, Ash's rivals might not take him as seriously at first when he's a girl, but he could prove them wrong with his skills.
If Team Rocket turns Ash into a Pokemon, his relationship with his old Pokemon would change. His Pokemon might not recognize him at first. But as they sense his familiar spirit, they could try to protect him. And Ash, in his new form, could learn a lot about the true nature of Pokemon. He could discover secrets about their evolution, abilities, and the hidden powers within them that he never knew as a human trainer.
Well, in this kind of fanfiction, Ash might take really good care of the egg. He could keep it warm and protected all the time. Maybe he'd build a special nest for it. And when it hatches, it could be a super powerful legendary Pokémon that immediately bonds with Ash and helps him in his Pokémon journey.