A plot idea might be that Harry's animal ears and tail are a side - effect of a powerful potion he drank by mistake. His friends notice the changes and at first are shocked but then become curious. They start to research in the library and find out that there's a way to turn these features on and off, but it requires a dangerous quest. So they all embark on this adventure together, facing various obstacles along the way, and in the end, they find the solution, and Harry has the choice to keep or get rid of his animal features.
One possible plot could be that Sesshomaru somehow ends up in the wizarding world of Harry Potter. Maybe a magical portal or a powerful spell goes wrong. He then has to navigate this new world with its own set of rules and magic, and he might encounter Harry and his friends.
One plot could be that Harry Potter is bitten by a vampire during one of his adventures outside Hogwarts. He then has to struggle with his new vampiric nature while still trying to protect the wizarding world from dark forces. Another idea is that there is a hidden vampire community within the wizarding world that Harry discovers, and he has to deal with the politics and secrets there.
His relationship with Hermione would likely change as she would be both intrigued and worried. She'd probably try to find a logical explanation and a solution right away. Ron, on the other hand, might be a bit more hesitant at first but would eventually come around and see it as just another strange thing in the wizarding world. His enemies, like Draco, might use it as a way to taunt him more, seeing it as a sign of his being different in an even more obvious way.
One possible plot idea could be how Snape deals with the physical and emotional changes during the pregnancy while still trying to maintain his role at Hogwarts. Another could be the reactions of other characters like Harry, Hermione, and Ron when they find out.
One possible plot could be that a Naruto character is transported to the Harry Potter world and has to let go of their chakra - based powers as they don't work there and learn magic instead, but they struggle with 'letting it die' i.e. their old way of fighting.
One plot idea could be that there is a strange magical - scientific anomaly that threatens both the wizarding world and the Watchmen's world. Harry and Jon have to team up to figure out what's going on and stop it. Maybe it involves a dark wizard using some sort of Watchmen - inspired technology to create chaos.
Maybe a fanfic where the Sorting Hat from Harry Potter is brought to Fairy Tail. The guild members could be sorted into Hogwarts houses based on their personalities. Natsu might be a Gryffindor because of his courage, while Lucy could be a Ravenclaw for her intelligence. This could lead to some interesting interactions and competitions within the guild as they explore the different aspects of the Hogwarts houses.
Maybe it could be due to a misfired spell in Hogwarts. Some student might accidentally cast a spell on Harry, and instead of the intended effect, it makes him grow a tail. It would be a really strange and comical situation for him.
One plot idea could be that Harry discovers he has bunny ears as a result of a misfired spell by a first - year student in the Hogwarts library. His friends are initially shocked but then find it hilarious. Another idea is that the bunny ears give him some special abilities, like being able to hear really faint magical sounds from far away. It could also be a part of a prank by the Weasley twins, who accidentally make the ears permanent on Harry and then have to figure out how to reverse it.
Well, one plot idea could be that Harry discovers he has a special gift for breeding magical animals that no one else has. He starts breeding rare and endangered magical creatures secretly in the Forbidden Forest. Eventually, his activities are discovered, but instead of getting in trouble, he is asked to help save the magical animal population in the wizarding world.