Yes, it's possible. Sirius is a popular character in the Harry Potter series, and many fans like to imagine him in different scenarios in fanfiction. He has a complex personality and a lot of untold stories, so fanfiction about him in the context of 'Prisoner of Azkaban' can be very interesting.
Sirius might be a bit angry if the fanfiction misrepresented him. He was a proud Gryffindor and a loyal friend. If the stories made him out to be something he wasn't, like a coward or a traitor in a different way than what was in the real story, he'd be offended. But on the other hand, if the fanfiction showed his true essence and added more depth to his relationships, he might be quite impressed.
One could also write a fanfiction about Sirius Black's impact on Hogwarts during the events of Prisoner of Azkaban. For instance, his presence, even though he's on the run, could have a big influence on the students. Some students might start to question the Ministry of Magic's actions, and Sirius could inspire them to fight for justice.
In many fanfictions about Sirius Black in Prisoner of Azkaban, he is often given a chance for a new adventure. Writers might imagine him escaping Azkaban in more elaborate ways, or having different interactions with Harry Potter and his friends. For example, some fanfictions have him forming a secret alliance with other prisoners to break out together.
It can change the canon story by adding new perspectives. The Marauders' view might reveal hidden details. For example, they could know secrets about Hogwarts' layout that affect the events in 'Prisoner of Azkaban'.
One common plot idea is exploring Sirius Black's life more in - depth. Maybe a fanfiction could focus on his time in Azkaban before his escape, showing his mental state and how he coped. Another idea is changing the roles. For instance, what if Hermione was the one who was wrongly accused instead of Sirius? It would create a whole new dynamic.
You can try some popular fanfiction websites like Fanfiction.net or Archive of Our Own (AO3). On Fanfiction.net, you can use the search bar and type in 'Prisoner of Azkaban' to get a list of relevant fanfictions. AO3 also has a great collection and advanced search options to help you narrow down to the exact type of fanfiction you're looking for based on tags such as characters, relationships, and genres.
One great fanfic could be 'The Lost Time in Azkaban'. It focuses on a new character who discovers a hidden mystery related to Sirius Black's time in Azkaban. Another is 'Hogwarts during the Prisoner's Threat' which delves into how the students' daily lives were affected by the news of the escaped prisoner. There's also 'A Different Perspective on the Prisoner' that tells the story from the point of view of a Hogwarts ghost.
Their relationship could develop as they study together for exams related to the 'Prisoner of Azkaban' events. For example, they might be researching about Animagi and in the process, discover new things about each other. This shared academic interest can bring them closer.
Well, fanfics enhance the experience in multiple ways. Firstly, they can fill in the gaps in the original story. In the Prisoner of Azkaban, there are parts that are left to the imagination, like what other students were thinking during the whole Sirius Black fiasco. Fanfics can answer those questions. Secondly, they can bring in new characters. These new characters can interact with the existing ones from the book, creating new storylines. For instance, a new student who has a special connection to the events in Azkaban. Thirdly, fanfics can change the tone. While the original story has a certain mood, a fanfic can be more light - hearted or more dark and gritty, depending on the author's vision. This gives readers a chance to see the Hogwarts of the Prisoner of Azkaban in different lights.
In some fanfictions, Harry might use powerful magic he's learned secretly. For example, he could discover a new spell that can break the Azkaban's defenses. He then sneaks into Azkaban, locates Sirius, and uses this spell to free him from his cell. Maybe he also has to fight off some Dementors on the way out.