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.
Perhaps the wings grow as a result of some ancient magic that has been awakened within Harry. He could be exploring an old, forgotten part of Hogwarts and accidentally triggers a spell or a curse that gives him wings. At first, he might be scared and try to hide them, but as he learns to control them, he realizes they can be used for good, like helping him rescue trapped students or animals in the Forbidden Forest.
There could be many amateur authors out there who might write such a fanfiction. It could be a young, creative Harry Potter fan who loves to imagine new and exciting adventures for the characters. They might be inspired by their love for the series and the idea of giving Harry a new and unique ability like growing wings.
One possibility could be that it's a result of some powerful magic gone awry. Maybe during a spellcasting class or an encounter with a mysterious magical artifact. This new development might lead to him being ostracized at first as others are afraid or jealous. But then he could use his angel wings to his advantage, like flying faster and more stealthily than on a broomstick.
Well, perhaps the plot could involve Harry suddenly waking up one day with butterfly wings. He'd have to figure out how to hide them at first, especially at Hogwarts. Maybe he discovers that the wings are a result of some new dark magic that was accidentally cast on him. He then goes on a journey to find a way to reverse it, all while trying not to let his friends know what's going on.
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.
In this fanfiction, Harry's butterfly wings might be a key to unlocking an ancient mystery at Hogwarts. The wings have special markings that match those on an old, forgotten tapestry in the castle. As he explores the meaning of these markings, he discovers that they are linked to a long - lost magic that was once used to protect the school. With his wings, he is able to access hidden chambers and passages that no one else can reach, leading to a series of exciting and dangerous escapades as he tries to piece together the mystery.
His mobility would change drastically. He could fly to class instead of walking, which would be a huge advantage in terms of time - saving, but also might get him in trouble with the school rules. For example, flying in the corridors is usually not allowed.
Maybe Harry is exploring an ancient and forgotten part of Hogwarts when he stumbles upon a magical artifact that causes him to build a cocoon. Once he grows wings from this cocoon, he finds that he has a connection to a long - lost race of magical beings with wings. He embarks on a journey to discover more about this race, all while trying to keep his new form a secret from his friends at Hogwarts who might be afraid of his transformation.
Maybe some of the Hogwarts professors like Professor Sprout. After all, she's the Herbology teacher. She could give Harry some expert advice on how to grow different kinds of food plants. She might even let him use some special greenhouses or tools in the school for his food - growing projects.