One interesting story could be where Harry discovers he has fangs due to a dark magic spell gone wrong. He has to hide it from his friends at first, but then they find out and help him find a way to reverse it.
In some fanfictions, Harry having fangs might be related to a new form of magic he uncovers. Maybe he's part of an ancient prophecy that involves this fang - like transformation, and he has to learn to control it to save the wizarding world. It could lead to some really exciting adventures and new friendships with magical creatures that are used to such features.
There could be a fanfiction where Harry gets fangs as a result of a magical experiment by a rogue wizard. He then finds that the fangs give him some unique abilities, like enhanced senses. However, the Ministry of Magic mistakes it for dark magic at first, and he has to prove his innocence while also dealing with the challenges of his new physical form.
A common reason could be a curse. Some dark wizard might have cursed Harry, and the fangs are a visible manifestation of that curse.
In some fanfictions, Harry's piercings might be related to a new fashion trend in the wizarding world. He could be at the forefront of this trend, with other students looking up to him. His piercings could also attract the attention of certain characters, like a love interest who is drawn to his edgy and modern look.
One possible story could be about Harry struggling to control his epilepsy while also dealing with the challenges at Hogwarts. Maybe he discovers a new spell or potion that helps him manage it better.
One interesting story could be about a young wizard who discovers a lost unicorn in the Forbidden Forest and forms an instant bond with it. The unicorn then becomes his familiar, guiding him through various magical challenges in Hogwarts, like helping him find hidden passages during the Triwizard Tournament.
In some of these fanfictions, the cat ears might be a result of a spell gone wrong. Maybe a mischievous student was trying to turn their pet cat into a human - like form but accidentally transferred some of the cat features to Harry instead. This would lead to a lot of chaos and hilarity as Harry tries to figure out how to reverse the spell while dealing with his new appearance.
Perhaps his wings are related to his connection with his Patronus. Since his Patronus is a stag, the wings could be like an extension of that magical energy. They might give him the ability to soar high above Hogwarts and keep an eye on the school grounds, almost like a guardian angel. He could use this newfound ability to sense danger from afar and protect his friends more effectively.
In some fanfictions, Harry's dyslexia could be a sign of his unique connection to the ancient magic. Since he is often at the center of extraordinary magical events, his dyslexia could be a part of what makes him special. It could be that the magic within him is so strong that it affects his perception of normal reading and writing in the Muggle sense.
One possible plotline could be Harry struggling to hide his Tourettes symptoms at Hogwarts in the beginning. He might be afraid of being judged by his classmates. For example, during a Potions class, his tics could cause him to accidentally add the wrong ingredient, leading to a minor magical mishap. Another plotline could involve Harry using his magical abilities to find a way to manage his Tourettes better. He could go on a quest to find a rare magical herb or spell that helps him control his tics. Also, his friends like Hermione and Ron could play a big role in supporting him, learning about Tourettes, and standing up for him when others are unkind.
In a fanfiction about Harry Potter having diabetes, there could be a plot where Harry discovers a new type of magic that is related to his condition. Maybe he finds that certain spells can help him better manage his blood sugar levels. His relationship with the Hogwarts staff could also be explored. For example, Madam Pomfrey might be at a loss at first as she's used to dealing with more typical wizarding ailments. But then she works with Harry to come up with a plan to keep his diabetes in check. This could also lead to a greater understanding of muggle diseases in the wizarding community.
In a more detailed plot, Harry's newfound eagle vision might be a side - effect of a powerful spell gone wrong. He initially struggles to control it, seeing things that are too far away or too detailed all at once. As he learns to master it, he realizes it gives him an edge in Quidditch. He can spot the Snitch from an incredibly long distance, making him an even more formidable Seeker. This also draws the attention of the opposing teams who try to find ways to counter his new ability.