Don't forget about the magical creatures that might exist in the same world. For example, a friendly witch who sometimes helps the little vampire out. Or a werewolf who is an unlikely ally during a time when both their species are in danger from a common enemy.
There could be a group of vampire hunters as characters. They are constantly on the lookout for the little vampire but never quite manage to catch him. And then there's the little vampire's family. His parents who are strict about vampire rules and his little sister who is always getting into trouble.
Well, of course, there's the little vampire himself. He could have a best friend who is a human, a brave kid who is not afraid of the vampire's nature. There might also be an old vampire mentor who teaches the little one about vampire traditions and how to control his thirst.
A young vampire who is new to the vampire queen's court. This vampire is naive and still learning about the ways of the vampire world. He could provide a different perspective and also be a source of trouble as he makes mistakes and the vampire queen has to deal with the consequences.
Naruto and Shinso are the primary ones. But we could also have an old and wise vampire elder as a main character. This elder could have knowledge about a prophecy that involves Naruto and Shinso, and his actions and decisions would drive a lot of the plot as he tries to either fulfill or prevent the prophecy.
Well, the little vampire himself is obviously a very popular character. He's the center of most of the stories.
Well, the little vampire himself is surely a main character. He's the one who drives most of the action in the fanfiction.
Obviously, the bumblebee itself is a main character. There could also be other insects like butterflies, ladybugs, and ants. Maybe a wise old spider who lives in a corner of the garden and gives advice to the bumblebee.
A wise old owl could be a new character. This owl could be the one who actually has knowledge about the real threats (or lack thereof) in their world. Maybe he tries to guide Chicken Little and the other animals. Another potential character could be a mischievous squirrel. The squirrel could be constantly causing small troubles that make Chicken Little think the sky is falling all over again. For example, it could knock down acorns that make loud noises.
A wise old sea turtle could be a new character. He could be the one who gives the mermaid advice about the human world and warns her of the potential dangers.
There could also be a character like a wise old vampire in the community who acts as a mentor to Rudolph, guiding him through the difficulties of being a young vampire in a world that has both vampire and human elements.
Obviously, the little vampire himself. He would be the main character with his unique vampire traits such as the ability to fly and his fangs.
The little vampire himself is often a very popular character. His struggle between his vampire nature and his friendship with humans makes him very interesting.