I think the wolf is the most interesting character in many ways. He's cunning and uses his wits to try and deceive Little Red Riding Hood. He represents the darker side of human nature or the unknown dangers in the world. In the bonus stories, there could be other characters that interact with the wolf in unique ways. For example, a brave woodsman who tries to outsmart the wolf. And of course, Little Red Riding Hood is also interesting as she has to grow and adapt during her encounter with the wolf and whatever else the bonus stories throw at her.
Well, Little Red Riding Hood herself is very interesting. She's this innocent girl who has an adventure that teaches her about the world. The wolf is also interesting as he is the main antagonist, very sly and devious. In the bonus stories, perhaps there are new characters like a wise old owl who gives advice to Little Red Riding Hood, which makes that character interesting as well.
The grandmother is an interesting character. She's a vulnerable figure in the original story, and in the bonus stories, we might get to see more of her backstory or how she deals with the whole wolf situation in different ways. Little Red Riding Hood is a classic character of interest too. Her journey from being a naive child to potentially learning some important lessons makes her engaging. And if there are any magical creatures in the bonus stories, like a helpful fairy, that would be a really interesting character as well.