It might be a way for the fanfic author to explore the concept of fame going to someone's head. Harry is famous in the wizarding world, and in fanfics, an arrogant portrayal could be a study of how that fame could potentially make him conceited. Also, it could be a reaction to the idea that in the original series, he sometimes got away with things because of his status as 'the Chosen One'. So, in fanfics, this could be exaggerated into arrogance.
One reason could be to create a new and different plot. By making Harry arrogant, the writer can show how his relationships with other characters change. For example, his friends might be less tolerant of him.
Well, it really depends on the specific fanfic. Some fanfic authors might decide to make Harry Potter arrogant for the sake of creating a different kind of story or exploring how such a change in his personality would affect the plot. But in the main series, he's far from arrogant. He grew up in difficult circumstances and that made him more empathetic and down - to - earth. So, in fanfics where he's arrogant, it's more of an author - imposed alteration for unique storytelling.
One possible reason is copyright infringement. Parseltongue is a unique creation within the Harry Potter series. If a fanfic uses it without permission while charging, it's likely violating the copyright of the original work.
One reason could be that the fanfic writer portrays Ron as overly jealous of Harry. In the original books, Ron has moments of jealousy but not to an extreme. If in the fanfic it's overdone, Harry might not be able to stand him. For example, if Ron is constantly trying to undermine Harry's achievements out of jealousy.
Often, it shows the characters being thankful for the things that are important in their world. Like they are thankful for their magical abilities. Harry could be thinking about how lucky he is to have his wand and be able to do magic, especially when he remembers his life before Hogwarts. The Thanksgiving theme just amplifies this sense of gratitude within the story.
In Harry Potter fanfic, monsters can be portrayed in various ways. Some are depicted as fearsome and menacing, like the traditional view of a werewolf during a full moon. They might be used to create suspense and danger in the story. For example, a basilisk could be lurking in the depths of Hogwarts, ready to petrify anyone who looks into its eyes.
Often, famine in Harry Potter fanfic can be a backdrop to show the social and economic disparities within the wizarding world. Some fanfic authors may depict poorer wizarding families or those on the outskirts of society suffering from famine while the wealthy or those closer to the Ministry seem unaffected. It could also be a factor in driving characters to make desperate choices, like joining a dark cause in exchange for food for their families.
In some Harry Potter fanfics, seduction might be portrayed through the use of magic. For example, a character could use a charm to make themselves more alluring. However, it's important to note that this often goes against the more innocent nature of the original series. Fanfic authors sometimes take creative liberties, but it can be a controversial topic among fans.
In fanfic, the Nundu is often portrayed as a huge, hulking beast with a menacing presence. It's shown as very powerful and its poisonous breath is usually emphasized.
In Harry Potter fanfic, elves are often portrayed in diverse ways. Some fanfics might expand on the house - elves like Dobby and Winky. They could be given more complex personalities, for example, an elf who is not only subservient but also has dreams of freedom and education. Some might show elves with magical abilities beyond what was shown in the original books, like the ability to transform into other creatures momentarily to escape danger.
It's often portrayed as a very alluring potion. In many fanfics, the description of its smell is really detailed. For instance, one character might smell freshly baked cookies (if they have a thing for food or a baker they like) and a particular type of flower that grows in a place special to them.