Often, the main character is the human who gets captured. They can be an ordinary person from our world who is suddenly thrust into the Pokémon universe and the strange situation of being inside a Pokeball.
Sometimes, there might be a Pokémon that plays a crucial role. Maybe it's a Pokémon that befriends the captured human inside the Pokeball, or a Pokémon that tries to help the human escape. It could also be a Pokémon that has some sort of special connection to the captor and influences their decision regarding the captured human.
Another concept is the relationship between the captor and the captured human. It's not just a simple master - servant relationship. There could be a lot of emotional complexity. The captor might feel guilty or conflicted, and the human might try to find ways to either escape or form an unexpected bond with the captor.
Often, the main character is a human or some other non - dark elf race who gets captured. Then there are usually the dark elves themselves, with their leaders or powerful warriors being important characters. Maybe there's a dark elf princess or prince who has a role in the captive's fate.
Thomas himself is obviously a main character. Often, his friends from the original Thomas world might be humanized too, like Percy and James. They usually play important roles in the fanfiction.
Often, there's a human protagonist who is somehow transported or finds their way into the dragon realms. This character is usually brave and curious, like a young adventurer. And then there are the dragons. There could be a wise old dragon that acts as a mentor to the human, guiding them through the strange new world. There might also be a dragon antagonist, one that sees humans as a threat and wants to drive them out of the realms.
In addition to the penguins, sometimes there are also human characters who play important roles. For instance, a kind - hearted scientist who discovers the penguins and tries to study them in a friendly way. Or a little boy or girl who befriends the penguins and helps them navigate the human world. These human characters interact with the penguins and add more depth to the story.
Naruto is usually one of the main characters, as it's in the title. He's the one being turned into or related to the 'human weapon' concept. Sasuke could also be a main character, perhaps being involved in Naruto's transformation or trying to stop it if it goes against their ideals.
Sometimes, there could be a mentor - like character for the human. This could be an old wizard or a wise being who has knowledge about the Storm King and the powers the human is acquiring. They guide the human through the difficult process of dealing with their new situation, teaching them how to control their powers and avoid the traps set by the Storm King or his minions.
Well, clearly Dory and Marlin are the main characters. They are the ones that the fanfiction usually revolves around. Dory with her forgetful yet endearing nature and Marlin with his over - protective and determined personality.
There can also be the scientist or inventor who is either responsible for the transformation or is trying to reverse it. This character adds a scientific aspect to the story and might have their own motives and secrets.
Well, obviously Megatron is a main character. In his human form, he's the center of the story. Often, there will be some human characters as well. Maybe a scientist who was involved in the process that turned him human, or a normal person who becomes his friend or ally.