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.
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.
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.
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.
In the original series, Hedwig is mainly a faithful owl companion. But in fanfiction, she can be much more. She could be a magical entity with her own backstory and motives. For instance, some fanfictions might explore her origin in more detail, like she was bred from a special line of owls with unique abilities.
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 fanfic, Harley Quinn can be portrayed with more emotional depth. While in the comics she's often a bit of a wild card, fanfic might explore her inner thoughts and feelings more. For example, her feelings towards Batgirl could be more nuanced, not just simple rivalry. Batgirl, on the other hand, can be shown to be more vulnerable in fanfic. In the comics, she's a tough crime - fighter, but in fanfic she might have moments of self - doubt, especially when dealing with Harley's unpredictable nature.
In fanfiction, Fem Harry might be more in touch with her emotions. While the original Harry was often a bit stoic, Fem Harry could be shown as more openly expressing her fears and joys. For example, when she is chosen for the Triwizard Tournament, she might have a more emotional reaction like crying out of a mix of shock and anxiety.
In some fanfictions, Molly Weasley might be portrayed as more of a mentor figure to characters other than her own children. For example, she could be shown guiding Harry through some complex magic that even Dumbledore hadn't thought of. This is different from the original series where her focus was mainly on her family and the Order's activities within that family - centric context.