The fat boy and the giant boy are surely the main characters. However, there could be other supporting characters that we don't know about yet. Maybe there are friends or foes of the fat boy and the giant boy that play important roles in the story as well.
The two obvious main characters are the fat boy and the giant boy. But think about it, there might be some hidden main characters too. For example, if the story is about a quest, there could be a wise old man who gives them guidance at the start, but still, the fat boy and the giant boy are at the center of the story. Their relationship, their actions, and their development are likely to be the focus of the 'fat boy giant boy story'.
Well, without more context, it's difficult to say precisely. It could be a story created by someone in a local community, maybe about how the fat boy and the giant boy overcame differences or challenges together. Maybe it has elements of friendship, where they learn from each other despite their physical differences.
The main characters are, of course, the giant and the little boy.
The main characters are the boy and the giant snake. The boy could be an ordinary child or someone with special qualities. The giant snake, on the other hand, could be a fearsome creature, but it may also have a complex personality. Their interactions, whether it's a conflict or an alliance, form the core of the story.
Since I don't really know the details of this story, I can't say exactly who Fat Boy is. He could be a friend of Billy Stewart, or a character created by Stewart for a specific purpose in the story.
As I haven't read the story, I can't say for sure. But likely there's the fat boy himself. There might also be his family members like his parents or siblings, and perhaps some friends or classmates.
Since we don't have much information, the main character could be an ordinary - looking boy from a small town. He might have a normal family, but something about him is special that leads to his growth. It could be his determination, his kindness, or some hidden talent that gets triggered and starts his growth journey, whether it's physical, mental, or emotional growth.
The tiny people themselves can be a group of main characters. Each tiny person could have their own personality, like a brave leader among them, a clever inventor, or a kind - hearted helper. And the giant boy is also a central character. His actions and decisions greatly affect the tiny people. For example, if he decides to move a big rock in his yard, it could either destroy the tiny people's home or open up a new area for them to explore. So he has a lot of power in the story, but also a lot of responsibility towards the tiny people.
Obviously, the main character is the boy who is getting fat.
As we don't know the exact 'fat boy expansion story', it's hard to determine the main character precisely. But if we go by the name, the main character is likely to be a boy who is referred to as 'fat boy' in the story.
Not having read the 'Fat Man and Little Boy Novel', if it follows the historical narrative, there could be characters representing the ordinary people affected by the development and dropping of the bombs. People in Hiroshima and Nagasaki who had their lives completely changed. These could be among the main characters as the novel might show the human side of this historical catastrophe.