Gengar. Although Gengar is a bit spooky, it has a soft heart deep down. It could adopt a human child who is not afraid of the dark. Gengar would then introduce the child to the nocturnal Pokemon world, showing the child how different Pokemon behave at night. It would be an interesting twist on the typical 'Pokemon adopts human child' story.
Squirtle. Squirtle is cute and friendly. If it adopted a human child, it could show the child the underwater world of Pokemon. The Squirtle could teach the child how to swim, and they could explore underwater caves together. It would be a really fun and light - hearted story with Squirtle as the main Pokemon.
If Ash adopts a child, the child could become friends with all of Ash's Pokemon pals. Pikachu could become like a big brother or protector to the child. Ash would have to balance his Pokemon training with taking care of the child. He might teach the child how to train Pokemon in a more gentle and understanding way, which could lead to new training techniques in the fanfiction.
In this fanfiction concept, Ash's adoption could be a very heartwarming story. Maybe he meets an orphaned child during his travels. Ash, with his kind heart, decides to take the child under his wing. It could be a chance for him to pass on his knowledge of Pokemon and values like friendship and perseverance.
Maybe a Pikachu adopts a human child. The Pikachu is part of a group of Pokemon that live near a human village. The child was abandoned, and the Pikachu takes it in. They go on adventures together, with the Pikachu protecting the child from other wild Pokemon and teaching it how to communicate with different Pokemon species.
It could be a scientist who is involved in the study of Pokemon genetics. While trying to understand the mechanics of evolution better, they accidentally stumble upon the new evolution and then become involved in the events that unfold as a result, both in the scientific and the trainer communities.
It could also be an experienced pokemon trainer who has seen a lot in their travels. After encountering a mirage pokemon by accident and realizing how different and powerful they are, they become determined to become the mastermind in the world of mirage pokemon. They use their existing pokemon training skills and knowledge to study these special pokemon, making them a formidable force in the fanfiction.
A young and curious trainer who has always been interested in the legends of Pokemon could be the main character. They might have heard rumors about the Hall of Origin and set out to find it.
The main character could be a talented pokemon stylist. They have a passion for making pokemon look their best with unique haircuts. They travel around different regions to learn new haircut techniques and to show off their skills on various pokemon.
It could be Ash. He's the classic Pokemon protagonist and has been through so many trials already. His will has been tested countless times, like when he faced the Elite Four or when he had to rescue his Pokemon from Team Rocket. In this fanfiction, he could face a new kind of test that really pushes his will to the limit.
A Pikachu could be a great main character. Pikachu is popular and has a lot of potential for character growth. It could start as a timid Pokemon but become a strong leader during the uprising.
To write a believable Pokemon child character, start by giving it unique traits. For example, if it's a Pikachu's child, it could have a slightly different color of its cheeks or a different pattern on its tail. Also, give it a distinct personality. Maybe it's more shy than the average Pikachu because it's still young and inexperienced. Make it have its own goals and desires, like wanting to explore a certain area of the forest that other Pokemon avoid.