Obviously, the little green pig is one of the main characters. It's the one that the story is centered around.
Perhaps there are also some human characters in the story. If it's a story where the pigs interact with the human world, the humans could be important characters. They might be the ones who first notice the little green pig's difference and react in different ways, which drives the plot forward.
In the 'little pig little pig story', the key characters are, of course, the little pigs. There are usually three of them. Each pig has its own personality which is reflected in how they build their houses. And then there is the big bad wolf. He is the antagonist. He is very sly and tries to catch the pigs for his meal. These characters together create the classic plot of the story.
The main characters are the three little pigs and the big bad wolf. The three little pigs are the protagonists who are trying to build their homes and protect themselves. The big bad wolf is the antagonist who tries to blow down their houses and eat them.
There are three little pigs, each with their own approach to building a house, and the big bad wolf. The pigs are different in their work ethic and decision - making when it comes to building shelters. The wolf, on the other hand, is the threat to the pigs' safety. He is greedy and uses his strength to try and get to the pigs.
Since I don't know the story, I can only guess. The main character is surely the little green dinosaur. There might also be other dinosaurs, like its parents or siblings.
There might be other animals too. For instance, a wise old owl could be another main character. The owl could give advice to the little green snake or help it out in some situations. And perhaps a friendly squirrel that befriends the snake and they have adventures together.
Since I don't know the story, it could be the owner of the little green tractor. Maybe it's a farmer.
Most likely, the main characters would be the fourth little pig, and probably the big bad wolf as in the original three little pigs story. There could also be the other three little pigs if they play a part in the story, either as friends or as characters that the fourth pig interacts with in some way.
Since I don't know the story, I can only guess. There must be the little green monster itself. Maybe there are other friendly or unfriendly creatures that it interacts with, like a wise old owl or a mischievous little rabbit.
The main character is Little Green Riding Hood herself. She is the one who sets out on the journey through the forest.
The wee little pig is the central character in this story. It is the one who undertakes the task of building the castle. Also, there's the big bad wolf. The wolf's role is to test the strength of the pig's castle. Without the wolf, the story would lack the conflict and the importance of the pig's castle - building efforts.