James Potter can be a popular choice too. His Animagus form was a stag. Fanfiction authors could write about his time at Hogwarts as an Animagus, his pranks with his friends in their animal forms, and how his Animagus abilities played a role in his relationship with Lily.
Minerva McGonagall is also a favorite. Her Animagus form of a cat gives a lot of room for creativity. Fanfictions might show her observing Hogwarts in her cat form, seeing things that she wouldn't as a human, and using that knowledge to protect the school and its students.
In many fanfictions, Sirius Black is still a very popular animagus character. His ability to transform into a dog makes for interesting interactions with magical creatures, especially those that are friendly to canines. Another popular one is Minerva McGonagall. Her animagus form of a cat allows for some really unique scenarios when she encounters magical cats or other feline - like magical creatures in fanfiction stories.
Obviously, Harry Potter would be one of the main characters. Since it's about him being an animagus.
Crookshanks is often a popular choice. In fanfiction, he might be given even more powers or a deeper backstory as a cat Animagus. Writers might explore his connection to Hermione in a more magical way, like he was sent to protect her all along as an Animagus.
Hermione Granger is often a popular choice. Fans like to imagine her as a multi animagus, perhaps as a fox for her intelligence and a deer for her grace. It gives her more depth and abilities in the fan - created stories.
Dumbledore could be his mentor. He has vast knowledge and experience, and he would likely see the potential in Harry being an Animagus. He could guide Harry through the difficult process of learning to control his transformation and use his Animagus form for good.
One popular theme is the discovery of being an Animagus. Many fanfics explore how a character suddenly realizes they have this ability and how they deal with it. For example, they might be scared at first but then learn to control it.
Ron Weasley could also be a main character. His loyalty to Harry would make him involved in the story. He might be there to support Harry, or perhaps even be a bit jealous of Harry's new ability at first but then come to terms with it and help Harry use it to their advantage in their adventures or against their enemies.
Obviously, Harry Potter is one of the main characters since it's in the title. He is the one with the animagus ability in this fanfiction.
In popular Harry Potter fanfiction, Animagus often play crucial roles. They can be used as a form of self - discovery for characters. For example, a character might learn more about their true nature through their Animagus form. Some fanfictions also use Animagus to bridge the gap between different magical communities. If a character is an Animagus, they can interact with both human wizards and the animal - based magical creatures in a different way. This can create a lot of interesting scenarios and storylines.
The 'Dragon Heart' series is quite popular. It features a complex plot where the dragon animagus plays a crucial role in a battle against an ancient evil. The character development in this fanfic is really good.