The main characters are obviously the three little sheep.
The characters are the three little sheep and the big bad wolf.
Well, in the three little sheep story, there are these three sheep. They go about building their own places to live. The first sheep is a bit lazy and builds a straw house quickly. The second sheep builds a stick house which is also not very sturdy. Then comes the wolf who wants to devour them. He blows down the straw and stick houses. However, the third sheep is clever and builds a brick house. So, when the wolf tries to blow it down, he fails and the three sheep are safe inside the brick house.
Well, the 'Three Little Sheep Story' might be about three little sheep. Maybe they go out to explore the meadow. One day, they face some challenges like a big bad wolf who wants to catch them. But the three little sheep are clever. They hide in a safe place or use their wits to outsmart the wolf. In the end, they continue to live happily in their meadow.
Typically, there are the little black sheep and the other regular - colored sheep. Maybe there could also be a shepherd.
Since I haven't read it, I can only guess. The main character is probably the sheep detective. There might also be other sheep in the flock that are either friends or suspects. And of course, there could be other animals on the farm like the farmer who might play a role in the story, either as a helper or someone who adds to the mystery.
Since I'm not sure which 'Sheep Boy Story' you're referring to, generally the main character would be the sheep boy himself. He is likely to be the central figure around whom the story revolves.
In a possible 'Christmas Sheep Story', the main characters could be a little lamb that is the bravest among the flock. Alongside it, there might be an old wise sheep that guides the others. There could also be some farm animals like a donkey and a cow that interact with the sheep during the Christmas events. Maybe there's a kind-hearted farmer who is also an important character as he provides shelter and food for the sheep during the cold Christmas.
The main characters in the Three Little Frogs story are simply the three frogs. They are the focus of the story. They could be named something cute like Greeny, Bluey, and Spotty. Their actions and relationships with one another drive the story forward. For instance, they might argue about which direction to go in their exploration, or they might support each other when facing a storm. Their little froggy world is full of these kinds of interactions and events that revolve around them as the main characters.
I have no idea about the 'three little pogs story', but if it follows a common pattern, the three little pogs are likely the main characters. They could be different in some ways, like one might be brave, one might be clever, and one might be kind. And perhaps there are other characters like an old wise animal that gives them advice or a big bad something that tries to cause trouble for them. But again, this is all just guesswork as I don't know the actual story.
There are three little monsters as the main characters. They could be different in appearance, like having different colors or shapes. And their personalities also vary. One might be shy, another bold, and the third curious. These differences in them make the story interesting as they interact with each other and the world around them.