His character arc can be very different. In the books, his development was somewhat limited, but in fanfiction, he could have a complete transformation. He might start to oppose the dark side more actively and become a hero - like figure, which is a big contrast to his original role.
In fanfiction, Dobby is often given more agency. In the original books, he is very much a servant - like figure at first. But in fanfictions, he can be a leader in the fight against the dark forces. For example, he might lead a group of house - elves in a rebellion against the Death Eaters who are cruel to them.
In the original books, goblins are mainly shown in relation to Gringotts Bank. But in fanfiction, they can have more diverse roles. They might be shown as having their own political agendas outside of the bank operations.
The power of augureys is often enhanced in fanfic. While in the books, their significance was somewhat limited. In fanfic, they might have the ability to heal with their feathers, or their song could have the power to put dark creatures to sleep. This expansion of their abilities makes them more interesting and central to the plot in many fan - created stories.
In the original books, Thestrals were not as prominently featured. But in fanfic, they can be the main focus. For instance, in some fanfic, Thestrals are shown to be more intelligent and able to communicate in ways not shown in the books.
Well, in fanfiction, Draco's arrogance from the books can be toned down a bit. He could be shown as secretly having a good heart all along. His snobbishness might be a front that he drops more quickly. Hermione's perfectionist streak can be exaggerated in some fanfictions. She might be even more obsessed with her studies and magic, but also more likely to let her guard down around Draco. And in fanfiction, their mutual understanding of each other's situations can be explored more deeply. For instance, Draco understanding Hermione's plight as a Muggle - born in a prejudiced wizarding world, and Hermione understanding Draco's family pressures.
In fanfiction, Newt can be more idealized. He might be shown as even more heroic than in the original. For example, his problem - solving skills could be enhanced. In the original, he has his limits, but in fanfiction, he may solve problems more quickly and efficiently. Also, his relationships might be more intense. His friendships could be deeper and his romantic relationships (if any) might be more passionate.
In the original series, squibs like Filch are more on the sidelines. But in fanfic, they can be the main focus. Fanfic might give them more agency and explore their unfulfilled magical desires more deeply.
One way it can be different in fanfic is in the control aspect. In the original series, legilimency was a complex and somewhat restricted magic. But in fanfic, a character might have perfect control over their legilimency, being able to turn it on and off at will, or even target specific thoughts within a person's mind with great precision.
In fanfiction, plants like the Mandrake might have different growth rates. For instance, instead of taking a certain number of months to mature as in the books, it could take years or just weeks. This change can be used to create unique plotlines, such as a wizard needing a fully grown Mandrake urgently but having to deal with the unexpected growth time.
Fuuinjutsu in Naruto fanfic often has different levels of complexity compared to the original. Fanfic writers may introduce new types of seals that have unique properties not seen in the show. For instance, a seal that can transfer a person's soul into another body. Also, the power levels of existing fuuinjutsu might be exaggerated in fanfic to create more intense storylines.