Maybe a new student, like a transfer from a different wizarding school. They don't know about the puking pastilles and get tricked into taking one. This new character could then be the main focus as they navigate through the puking chaos and also learn about the unique culture of Hogwarts.
Fred or George Weasley would also make great main characters. They are the pranksters of Hogwarts, and it would be in character for them to either create their own version of the puking pastilles or use the existing ones in a wild and elaborate prank that goes wrong in the most entertaining ways.
A really interesting plot could be that the puking pastilles are actually part of an ancient wizarding recipe that was lost. A group of students find an old book with the recipe and decide to recreate the puking pastilles. But they accidentally create a super - powerful version that not only makes people puke but also causes other strange magical effects like making objects float while puking. This then leads to a race against time to find an antidote before the whole school is in complete disarray.
It could be a new character, like a young Auror who has been assigned as an inspector. He would be fresh out of training and eager to prove himself at Hogwarts. He might be a bit naive at first but quickly learns the ropes and uncovers some interesting things about the school.
It could be a young witch who is just starting to explore her magical abilities outside of Hogwarts. She takes on a babysitting job to earn some extra money and ends up having all sorts of magical adventures with the kids she babysits.
A new character could be the main character. For instance, a Saiyan who has been transported to the Harry Potter universe. This character would have to navigate the strange new world of magic while also dealing with their own Saiyan instincts and powers.
It might also be a descendant of one of the well - known characters from the Harry Potter series. For example, a grandchild of Sirius Black who inherits his rebellious spirit and uses it to fight against the new dark forces as the 'darkslayer'.
A new student at Hogwarts could be the main character. They might be a bit of an outcast and find solace in the graveyard. There, they stumble upon a mystery that no one else has noticed before, and it becomes their mission to solve it. This would be a great way to introduce a fresh perspective to the Harry Potter fanfic world.
It could be a long - lost relative of Harry Potter. Maybe a cousin who was hidden away for some reason and now discovers their magical heritage. They could have a different personality from Harry, like being more shy and studious but still having a great sense of justice.
Obviously, Harry Potter himself could be the main character. Given his adventurous nature, he would be a great fit to incorporate parkour into his already impressive list of skills. He could use parkour to explore new areas of Hogwarts or to escape from dangerous situations.
Neville could also be a main character. He's often underestimated, but if he found the Harry Potter headphones, it could be his chance to shine. He could use the power of the headphones, whatever it may be, to stand up to bullies or to help protect Hogwarts. Maybe the headphones give him the confidence he needs to become a hero in his own right.
A Muggle - born wizard could be the main character. They are used to the Muggle concept of hairdressing but also want to incorporate their new - found magic into it. This character would be constantly trying to bridge the gap between the two worlds in their salon, creating a unique blend of Muggle and wizarding hairdressing styles.