Luna would likely have a very unique reaction. She might say that the fanfiction is just another form of magic in the world of imagination. She could tell Harry that he should embrace it in a way, as it shows how much people are interested in his story, even if it is a bit mortifying at first. But she would also respect if he was really bothered by it.
At first, his friends would be shocked. Hermione might think it's some kind of dark magic at first glance. But as Harry shows them what he can do, she would start to analyze it scientifically. Ron would be more awed. He'd be like a kid seeing a new cool trick. They would both support Harry in exploring this new ability, but also be a bit cautious as they don't fully understand where it comes from or what the implications are in their wizarding world.
His friends would be very surprised. Hermione would probably be a bit skeptical at first. She'd want to research all about Witchers before she fully supported Harry's new interest. Ron, on the other hand, might be more excited. He'd see it as another adventure and would be eager to hear all about the Witcher world from Harry.
Ron would probably be both shocked and a bit awestruck at first. He might make some typical Ron - like jokes to ease the tension, like 'Blimey, Harry, you're a dragon! At least you'll be good for scaring off Snape now!'. But deep down, he'd be worried and determined to help Harry get back to normal.
His friends would be quite shocked. Neville might be a bit scared at first, thinking it's some new dark magic. But then they'd all come together. Ginny would probably be the one to try and comfort 'cat - Harry' by giving him some fish or milk, thinking that's what cats like. And they'd all be determined to get him back to normal as soon as possible.
At first, Harry would be in disbelief. He would think it was some sort of joke or misunderstanding. But as the reality sets in, he would become a bit of a loner. He'd still have his sense of right and wrong, so he might continue to fight against the dark forces on his own, all the while hoping that his friends would come to their senses and realize they made a huge mistake in betraying him.
Hermione would probably be both curious and concerned. She'd want to research immediately to find out how and why this happened. Ron, on the other hand, might be a bit more in awe at first. He'd likely make some jokes about Harry looking like a strange bird, but still be supportive.
Hermione would probably be quite understanding. She might see it as an opportunity to promote equality and acceptance in the wizarding world. Ron, on the other hand, would likely be a bit more awkward at first, but would soon come around to support Harry once he realizes it's not a big deal.
The Weasley twins would absolutely love it. They'd see it as a great opportunity for more pranks. They might magically enhance the dress to do all sorts of crazy things, like change colors or play music, all while Harry is trying to go about his normal day at Hogwarts. And they'd be very protective of Harry if anyone made mean comments about his dress - wearing.
Hermione would probably be very curious at first. She'd immediately start looking through all her books to find any information about such a strange transformation. Ron, on the other hand, might be a bit more freaked out. He'd probably make some jokes at first to cover up his unease, but then he'd be there to support Harry. Ginny would likely be concerned but also find it kind of cool and would try to help Harry get used to his new wings.
He might be very sad at first. Harry has always valued his friends, so being forgotten by them would be a huge blow.