Well, obviously Harry is the main character. He is the one with the monstrous side. And often, his friends like Ron and Hermione are also important characters as they might either help him or be in the dark about his true nature.
Sometimes, characters from the original series in different roles. For instance, Dumbledore could play a more complex role, either trying to protect Harry's secret or having his own motives regarding Harry's monster nature. The fanfic may also introduce some magical creatures as side characters that are related to Harry's monstrosity in some way.
In some fanfics, there could be new characters introduced. For example, a mentor figure who knows about Harry's monstrosity and guides him on how to handle it. Or there could be antagonists who are out to expose Harry or use his monster side for their own evil purposes.
A group of students from different houses could be the main characters. For example, a Gryffindor boy who is curious about the mystery of monster girls, a Ravenclaw girl who has extensive knowledge about the Forbidden Forest where some monster girls are rumored to live, and a Hufflepuff boy who is always ready to stand up for the underdog, which in this case are the monster girls. They join forces on a quest that changes their view of the wizarding world.
A delivery driver who drinks Monster Ultra to keep up with the fast - paced work. He might encounter all sorts of interesting characters during his deliveries and have some exciting adventures, so he could be a great main character. He could also have a backstory about why he took up this job and how Monster Ultra has become an essential part of his daily routine.
Since I haven't read this particular fanfic, it's hard to say for sure. But it could feature Naruto himself as he often has to deal with various threats in fanfics. Or perhaps it could focus on a new character that the author has created who is the so - called'real monster'.
Since I haven't read it, it's hard to say. But it could feature the main characters from Twilight like Bella, Edward, or Jacob, with one of them being the focus as the one with the 'monster' inside.
It depends on the specific fanfic, but often it could include Naruto - like characters who have the shifter ability. Maybe Naruto himself could be a shifter in some versions, or new original characters created specifically for the fanfic.
Well, aside from Bill and Dipper, Mabel might also make an appearance in some 'billdip monster falls fanfic'. She can add an extra layer of humor and sisterly love to the story. Sometimes, other characters from the original series like Soos or Wendy might also be included, but they usually play supporting roles compared to Bill and Dipper.
Smith Lemon is surely a main character. Then, depending on the fanfic's focus, it could be a mermaid - like monster musume. She could bring a sense of mystery as she is from the underwater world. There might also be a centaur - type character who is strong and has a noble personality. All of these characters, along with Smith Lemon, would play important roles in the story, each with their own goals and personalities that collide and interact.
Obviously Naruto is one of the main characters. He's likely the central figure around which the story of the ranch and the monster girls revolves. His ninja skills and personality traits would play a big role in how he manages the ranch.
In 'Harry and Teddy fanfic', the two main characters are Harry and Teddy. Harry is the one who has been through so much in the wizarding world. He has a sense of responsibility towards Teddy. Teddy is a character full of possibilities. He's the product of a tragic event (his parents' death), and Harry's presence in his life is like a guiding light. Their personalities, Harry's wisdom and Teddy's eagerness to learn, are often explored in these fanfics, which makes for very engaging stories.
In some fanfics, there could be magical animals other than crows. For instance, a wise old owl that serves as a mentor to Harry. The owl could give Harry advice on how to deal with various situations, such as when he is facing a difficult choice or when he is in danger. These additional characters add more depth and variety to the fanfic stories.