Draco would likely be disdainful at first. He has a high opinion of himself and might not like how some fanfictions depict him. Harry might be more curious and open to it, as he's always been more accepting of different ideas.
Draco might be appalled if he reads fanfiction that doesn't uphold his pure - blood ideals. He could also be a bit flustered if he reads about relationships with characters he doesn't expect. Harry would probably find it fascinating. He'd enjoy seeing the different takes on his adventures and relationships, and might even be amused by some of the more outlandish ideas.
They might be shocked at first. I mean, seeing their own stories being written in a different way by fans would be quite unexpected. Sirius might find it really cool and be eager to read more, while James could be a bit more critical, thinking about how accurate the portrayal is. Remus would probably be more laid - back and just enjoy the different interpretations.
For Harry Potter characters, reading fanfiction could be a strange experience. Ginny might be protective of how she and Harry are portrayed in romantic fanfictions. Neville could be surprised by the confidence some fanfictions give him. In RWBY, Blake might be a bit hesitant at first but then get into the more thought - provoking fanfictions. Pyrrha, if she were still alive, would likely be flattered by the positive portrayals in fanfiction. It would open up a whole new world of how they are perceived by their fans for all of these characters.
Yang would likely have a big reaction. If the fanfiction shows her in a cool fight scene, she'd be all for it and might even show it off to her friends. But if it portrays her in a negative or weak way, she'd be really annoyed.
Some characters might be flattered. If they are depicted as heroes in the fanfiction, it would boost their egos. For instance, Oliver Queen might enjoy reading about himself as an even greater hero than he already is.
Percy would probably find it hilarious. He has a good sense of humor and would likely enjoy the wild and crazy scenarios fans come up with. He might even share the funnier ones with his friends at Camp Half - Blood.
Naruto, being the open - minded and adventurous type, would likely find it fun to read fanfiction about himself. He could be amused by the creative ideas, even if some are a bit far - fetched. He might even take some of the positive ideas and think about applying them in his real adventures. Rias, however, would approach it more skeptically. As a devil princess, she has a reputation to uphold. She would carefully analyze how the fanfiction portrays her, and if it goes against her values or the image she wants to project, she might be a bit offended. But if there are some good aspects, like new ways of handling her devil powers or relationships, she might consider them.
Naruto would be thrilled. He loves attention and the idea that people are writing stories about him would make him feel really special. He might even try to find the authors and befriend them.
Apollo would probably love it. Since he is the god of poetry and creativity, he'd be intrigued by the different interpretations of himself in fanfiction. He might even get some new inspiration for his own creative works from it.
There are also those who would be intrigued. Clary, being the curious one, would probably read fanfiction with great interest. She might be amazed at the different ways fans have imagined the story continuing or the relationships evolving. She could even get some inspiration from it for her own adventures, thinking about how the fans' ideas could be incorporated into her real - life challenges in the Shadowhunter world.
Draco would probably be extremely angry. He might feel a deep sense of hurt and betrayal, especially if he considered Harry a friend or at least an acquaintance he could trust. He could start plotting revenge against Harry, using his own cunning and Slytherin skills to make Harry's life difficult at Hogwarts.