Obviously, Draco Malfoy is the central character since he's the one who turns into a ferret. Harry Potter often appears as well, as he has a history of conflict with Draco. Hermione Granger might also be there, perhaps using her knowledge to try and figure out a way to turn Draco back. Ron Weasley could be included too, probably making some snide remarks about Draco's new form.
Well, in some 'Draco turned into a ferret fanfiction', there could be a plot where Draco in ferret form discovers new things about the Hogwarts grounds that he never noticed as a human. Maybe he stumbles upon a secret passage or a hidden magical creature. Also, there could be a story where his transformation is a result of a misfired spell by a student, and the whole school has to figure out how to reverse it.
It could be Draco Malfoy. Maybe he somehow manages to use a new spell or a dark object to turn Harry into a ferret out of spite. He might then try to keep Harry in that form to humiliate him in front of the whole school.
Perhaps there's a plotline where the transformation into a ferret has some unforeseen side effects. For example, Harry might gain some ferret - like abilities such as enhanced sense of smell or speed, which he then uses to his advantage in solving a mystery or escaping from a dangerous situation in Hogwarts. He could also struggle with some of the more ferret - like instincts, like being tempted to hoard shiny objects.
One interesting 'Harry Potter Ferret' fanfiction could be one where the ferret transformation of Draco Malfoy is explored in more depth. It might focus on his thoughts and feelings during that time, adding new dimensions to his character.
Well, at first, Harry is just doing his duty to take care of Draco in his ferret form. But as time passes, they start to communicate in a different way. Draco, unable to be his usual snarky self as a ferret, has to rely on Harry. Harry realizes that Draco isn't all bad, and Draco, in turn, sees Harry's kindness. So, their relationship evolves into a more friendly and trusting one.
One interesting plotline could be that Harry discovers Draco in his ferret form injured in the Forbidden Forest. He decides to take care of him secretly in his dormitory. As he nurses Draco back to health, they start to understand each other better, breaking down the long - held grudges between them.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of Harry Potter fanfictions, and you can easily search for ones related to the ferret incident. Just use the search bar and type in relevant keywords like 'Harry Potter Ferret' and browse through the results.
Their relationship would likely become more complex. Draco, who was used to taunting Harry as a boy, might be more hesitant to do so when Harry is a girl. He could be thrown off by her new appearance and find it harder to be as cruel. There might be a sense of confusion in him.
The main characters are Harry and Draco. Harry, now in a female form, is the center of the story as he experiences a whole new way of life at Hogwarts. Draco, on the other hand, is the catalyst for this change. He is likely to be a central figure as he either tries to reverse what he's done or deal with the new situation he has created. There may also be other important characters like Hermione and Ron, who are Harry's friends and will be involved in his new journey.