The characters in Harry Potter would likely be very shocked at first. Hermione would probably start researching immediately to figure out what Michael Myers is. Harry might be more cautious, ready to defend himself with his wand. Ron would probably be a bit scared but try to act brave. They would all have to use their unique skills and magic to deal with this new and unexpected threat.
If Michael Myers showed up in the wizarding world, Harry Potter would probably see him as another dark entity to defeat. He'd rely on his courage and the training he's had from Dumbledore and his friends. Hermione would use her vast knowledge of magic to try and find a way to stop Michael Myers. For example, she might look into spells that could trap or immobilize him. Ron would be there for support, using his Weasley family's unique magic items if needed. They would all come together, just like they did against Voldemort, to face this new danger.
It could be a really strange and unique blend. Maybe Michael Myers somehow finds his way into the wizarding world of Harry Potter. He could be a dark force that the Hogwarts students have to face, using their magic in ways they never thought before to stop him. It would be a clash of two very different horror and fantasy elements.
For Freddy Krueger, you could explore his backstory more deeply. Maybe in the fanfiction, he has moments of self - doubt about his actions, which is a new side to him. As for Michael Myers, you could develop his relationship with his mask. Show how it's not just a tool for him, but almost like a part of his identity. You could also have them interact with other characters in ways that force them to change. For example, if they meet a strong - willed survivor, it could make them question their methods of killing.
The ponies might initially react with fear when they see Michael Myers. They could run away or try to hide. But some braver ponies, like Rainbow Dash, might try to confront him. Michael Myers, on the other hand, could be indifferent to the ponies at first. As the story progresses, they could start to communicate through simple gestures if Michael Myers doesn't speak. For example, the ponies could offer him food to show friendship.
Fanfiction expands on their characters by giving them more backstory. For Laurie, it could be about her life before the events that made her Michael's target. It might explore her family history, her dreams, and how all of that shapes her in the face of Michael's threat. For Michael, it could go deeper into his origin, perhaps exploring if there was a trigger that made him into the killer he is. This gives more depth to their characters than what is shown in the original movies.
Some characters might be excited. They could see him as a new source of knowledge and magic.
The Weasley family would have different responses. Mrs. Weasley would be motherly and concerned about this strange new person. Fred and George would see her as a source of new ideas for their pranks and inventions. Ginny would look up to her as a strong female figure, much like she does with Hermione. And all of them together would gradually get used to having Powergirl around, and they would all grow from the experience of interacting with someone from a completely different world.
Batman would probably be very cautious at first. He'd want to study Harry and his magic to see if it could be a threat or an asset. The Joker might see Harry as a new plaything, a strange and magical being to toy with. Commissioner Gordon would likely be intrigued and hope that Harry could help clean up Gotham's streets.
Some characters might be quite amused. For example, Hermione would probably analyze the fanfiction from a logical perspective, critiquing the plotlines that involve ships. Ron, on the other hand, might be a bit bewildered at first but then find it rather entertaining. Harry himself could be either indifferent or intrigued, depending on how the ships are portrayed. If it's a ship that he has a personal connection to, like his parents, he might be more interested in seeing how the author has envisioned their relationship in the fanfiction world.
Dumbledore would likely be very accepting of Stitch. He has a great understanding of all kinds of creatures and beings. He would see Stitch's potential for good and might even try to find a place for him at Hogwarts. Snape, however, would be more skeptical. He would keep a close eye on Stitch, worried that he might disrupt the order of the school or cause harm to the students. The Weasley twins would probably find Stitch hilarious and would want to play pranks with him or use his unique abilities for their own mischievous plans.
Draco Malfoy would probably be outraged at first if he read fanfiction that showed him in a positive light towards Harry and his friends. He's so used to being on the opposite side, but then he might secretly be a bit flattered by some of the more complex characterizations of him.