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.
In many 'naruto human weapon fanfiction' stories, Hinata could be a main character. Given her feelings for Naruto, she might be deeply affected by Naruto becoming a 'human weapon'. She could be part of the group that tries to protect Naruto from those who want to misuse his new - found power. Additionally, Orochimaru might also be a main character as he is always interested in powerful things and might want to either control or study Naruto as a 'human weapon'.
Often, Kakashi can be a main character in this type of fanfiction. He has a lot of knowledge and experience, so he might be the one trying to guide Naruto through the process of becoming a 'human weapon' in a more positive way, or he could be trying to prevent it if he thinks it's too dangerous. Another character could be Jiraiya. Since he was Naruto's mentor, he might play a crucial role in how Naruto's 'human weapon' status develops.
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.
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.
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.
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.
The main characters are often Naruto, as he is the focus of the mecha concept. Shikamaru could also be a main character in this type of fanfiction. He would be the strategist, trying to figure out how to best utilize the mecha Naruto in battles. Additionally, Orochimaru might be a character in some cases. He could be interested in stealing the technology of the mecha for his own evil purposes or trying to manipulate Naruto through it.
Obviously, Naruto and Matsuri are main characters. Naruto, with his energetic and determined personality, often drives the story forward. Matsuri, being from Suna, brings a different perspective to the story. Sometimes, other characters like Sakura or Kakashi might also make an appearance to add more depth to the plot.