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.
Obviously, Harry Potter would be one of the main characters since it's about him being a multi animagus.
One popular example could be 'The Hidden Abilities' where Harry discovers he is a multi - animagus early on. It changes the whole dynamic of the story as he has to learn to control his different forms and hide this from Voldemort. Another is 'A Different Kind of Magic' which focuses on how being a multi - animagus affects his relationships with his friends like Ron and Hermione. They are both amazed and a bit worried at first about this new aspect of Harry.
Friendship is also a big theme. His friends usually play a role in his journey to becoming a multi animagus. They might help him train or be there to support him when things go wrong. For example, Hermione could use her vast knowledge to assist Harry in understanding the complex magic involved. And Ron could be there for moral support.
One interesting aspect could be seeing Harry Potter transform into different animals in new and creative ways. It might also explore how his relationships change due to this new ability.
One interesting concept could be characters having multiple animagus forms. For example, a character might be able to transform into a bird and a cat. This could add new layers to the story, like how they use different forms for different tasks or to solve mysteries.
One common theme is self - discovery. Characters often find out about their multi - animagus abilities and in the process, learn more about themselves, their strengths, and weaknesses. For example, they might realize they have a connection to certain animals that reflects their personality traits.
With Harry and Ron, it might strengthen their bond. They would be in awe of her new ability and it could add an extra layer of protection in their adventures. For example, if she could transform into a bird, she could scout ahead for danger more easily.
Harry Potter himself is of course very popular. Writers often explore his life further, like his post - Hogwarts years. Hermione Granger is also a common feature. Fanfiction might show her in different academic pursuits or her relationships. Draco Malfoy is another one. He has a complex character, and fanfictions can explore his redemption arcs or his relationships with other characters in more depth.
One great 'Harry multi animagus fanfiction' is 'Harry Potter and the Animagus Secret'. It has an interesting plot where Harry discovers his multiple animagus forms in a very unexpected way, with lots of adventure and mystery along the way.
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.