Obviously, Danny is a main character. He has to deal with the effects of the Blood Blossoms on his powers and his life.
The main character is Danny Phantom without a doubt. He is the driving force behind the pirate radio. His friends play important roles too. Tucker Foley, who is good with computers and technology, helps with the technical aspects of running the radio. Sam Manson, being Danny's closest friend and having a strong personality, might be involved in choosing the content or dealing with any moral or ethical issues related to the radio. And then there are the ghosts that Danny has to deal with on a regular basis, which could include Skulker or Ember, who might either be interested in the radio or try to cause trouble for Danny.
Jazz, Danny's sister, is also a common character. She might be the one who tries to understand Danny on a more emotional level when the power of the Ghostly Wail starts to take a toll on his mental state. For example, she could be the one to talk him down when he's frustrated about not being able to control it properly.
Well, Danny Phantom himself is obviously a main character. He's the half - ghost hero. And then, members of the Ember family are also often in these fanfictions. Ember McLain is a popular character from the Ember family. She has her own powers and a unique personality.
Another common character is the antagonist. It could be a powerful dark sorcerer who wants to steal the Brown Phantom's powers or use them for evil purposes. Their clashes are often the highlight of the fanfiction.
Obviously, Danny Phantom is one of the main characters. He's the hero with his ghost - fighting abilities and dual identity.
Tucker Foley and Sam Manson are also often main characters. They are Danny's best friends in both his human and ghost - fighting life, so they play important roles in many fanfictions. They might be helping Danny deal with the challenges of his dual identity or getting involved in his battles against ghosts.
Some fanfictions might also feature the prison guards as main characters. They could be complex characters with their own motives and backstories, and their interactions with Naruto could drive the plot forward. For example, a guard who initially sees Naruto as just another prisoner but then comes to respect him.
Often, Naruto himself can be a main character in these fanfictions, especially if the story is about him discovering he has some sort of royal blood. Sasuke is also a popular choice as he has a powerful and complex backstory that can be intertwined with the concept of royal blood.
One interesting idea could be exploring how the Blood Blossoms affect Danny's powers in unique ways. Maybe they don't just weaken him but also cause some strange glitches in his ghost form.
There could be some ghost characters involved too. For instance, Vlad Masters might show up in the fanfiction. He could be either jealous of Danny's new ability with the claws or try to use it to his own advantage. Another character could be Skulker. He might see Danny's claws as a new trophy to hunt for, which would lead to some exciting chase scenes in the fanfiction.