Friendship is a very common theme. They are often portrayed as having a deep bond that goes beyond just being teammates in Quidditch.
A big theme is determination. Both Harry and Oliver are very determined characters in the original series, and this is often emphasized in the fanfiction. They strive for victory in Quidditch and also in other aspects of their Hogwarts life. Also, loyalty is quite common. Their loyalty to their team, Gryffindor, and to each other is often explored in different ways, like standing up for each other against rival teams or dealing with internal house issues.
Romance is likely a very common theme. Writers might explore how Harry and Lisa could fall in love, perhaps over coming cultural or world - view differences. They could start off as strangers and gradually develop feelings for each other through shared experiences in a new, made - up world.
Another theme is self - discovery. Harry and Cho are both at an age where they're still figuring out who they are. Fanfics often explore how their relationship helps them in this journey, like Harry becoming more in touch with his emotions through his interactions with Cho.
Another theme is self - discovery. The characters of Harry and Louis are often on a journey of self - discovery in relation to their feelings for each other. In some fanfics, they have to figure out who they are and what they really want in terms of their relationship.
One common theme is the exploration of family bonds. Since James is Harry's father, many fanfics focus on how they could have interacted if James had been alive. Another theme is the passing on of knowledge or skills from father to son.
One common theme is friendship. Since both Luna and Harry are unique characters in the Harry Potter universe, their friendship is often explored in fanfics. Another theme is the discovery of hidden magic. Luna's penchant for the strange and unknown often leads them to find new magical things together.
Rebellion against the status quo can also be a theme. Sirius is a bit of a rebel, and he encourages Harry to question things. So in many fanfics, they might be involved in actions that go against the traditional rules of the wizarding society. And of course, the theme of friendship - a deep, unbreakable friendship that could be seen as more than just friendship in some interpretations.
One common theme is friendship. Since they may come from different backgrounds, the fanfics often explore how they become friends. For example, they might have to overcome initial misunderstandings.
One of the main themes is protection. Harry might feel the need to protect his sister from the dangers that lurk in the magical realm, like the dark wizards. Friendship can also be a theme as the sister might make new friends at Hogwarts, and Harry has to deal with his feelings about that. Also, self - discovery is common. The sister may be finding out who she really is and Harry is there to support her in that journey.
The theme of power dynamics is also common. Harry being the 'Chosen One' and Draco from a powerful pure - blood family creates an interesting power dynamic. Fanfics often explore how this affects their relationship, whether they use it to push each other away or come closer together.