I don't know for sure, but probably the children themselves are main characters. And of course, the rats.
In 'the rats came back children's story', the main characters are likely to be the children. They could be a group of friends who discover the rats' return. These children might have different personalities, like a brave one, a curious one, and a cautious one. The rats are also main characters. They could have their own little rat society within the story. There may also be some secondary characters such as pets in the children's home that react to the presence of the rats. For example, a cat that gets excited by the return of the rats or a dog that is protective of the children.
I'm not sure specifically as I haven't read this exact story. But generally, it might be about rats that were once gone and then returned, perhaps causing some sort of trouble or adventure in a place where children are involved.
The main character is surely the cat. There might also be the cat's owner or the people in the household where the cat belongs.
Since I don't know the exact 'rats short story', it could be the rats themselves. Maybe there's a brave rat that leads the group, or a young rat that is learning about the world around it.
Since I don't know the exact 'ghost rats story', it could be the rats themselves as the main characters. They might be led by a particularly large or intelligent 'ghost rat'.
I don't know as I haven't read the novel. It could be a couple who had a history together, like a young man and a young woman who were once in love in high school or college.
The main character is the man who decides to rob the graves in the graveyard full of rats.
Based on the title, the main characters are likely to be rats. And since it's about a 'new cap', perhaps the cap could also be considered a sort of character in the sense that it has an impact on the rats' story.
Most likely the two lab rats in love are the main characters. But there could also be some supporting characters like the scientists who take care of them or other lab animals.
The main characters in this 'a village full of rats story' are the villagers for sure. They are the ones facing the situation of a rat - filled village. But also, there might be a character like a clever hunter or a wise old woman in the village. The hunter could be trying to catch the rats in his own creative ways, like using special traps or his hunting skills. And the old woman might have some traditional knowledge about how to keep rats away, like using certain herbs or making specific noises. So these could be the main characters in the story.
Since I haven't read the novel, I can't say for sure. But I would assume the main character is the woman who comes back as a war goddess. There might also be characters like her friends or family from her previous life who play important roles in the story, or maybe other deities or powerful warriors who interact with her in her new form.