Well, Vlad Masters is quite popular too. He has his own complex backstory and relationship with Danny, and in fanfiction, his character can be explored further. He can be an antagonist, or sometimes, writers might even create a scenario where he teams up with Danny or Dan. And then there's Sam and Tucker, Danny's friends. Their loyalty and the different skills they bring to the table make them interesting characters in fanfiction.
Obviously, Danny and Dan themselves are very popular. Danny as the main hero and Dan as his dark and complex counterpart are central to many stories. Jazz, Danny's sister, is also popular as she can provide a different perspective and often gets involved in Danny's ghost - fighting adventures in fanfiction.
Clockwork is also a beloved character in Danny Phantom and Dan Phantom fanfiction. His time - traveling abilities open up a whole new realm of possibilities. Writers can use him to create really interesting plot twists, like sending Danny or Dan to different points in time to change their fates. His mysterious nature also makes him a character that readers are eager to see more of in fanfiction.
Obviously, Danny Phantom and Dan Phantom are the main characters. Danny is the original form, a heroic character, and Dan is his more evil and powerful transformation.
Well, in some fanfictions, there are concepts like redemption arcs for Dan Phantom. It's fascinating to see how writers try to redeem such an evil character. Also, the idea of Danny using Dan's power for good in some unique situations. For example, there could be a story where Danny has to borrow Dan's strength temporarily to defeat a powerful ghost that he couldn't handle on his own.
Obviously, Danny Phantom is the main character as it's about his transformation into Dan. His friends like Sam and Tucker would also be important characters. They would likely play a role in trying to either stop the transformation or help Danny deal with the consequences. And of course, his ghostly foes might also be involved, as they could either take advantage of his situation or be affected by the power shift if he becomes Dan.
Well, they might share some physical characteristics. Maybe in the fanfiction, Dan has the same white hair or green eyes as Danny Phantom. Also, their powers could be depicted in a similar way, like the ability to go intangible or fly.
Sam and Tucker are also quite popular. They often play important roles in helping Danny deal with his TG (transformation - related) situations. Sam might use her goth knowledge or her strong will to assist Danny, while Tucker uses his tech - savvy skills.
Danny Phantom himself is obviously a very popular character in these fanfictions. He is the main character and his dual identity as a human and a ghost brings a lot of interesting elements to the racing scenarios. His ability to transform and use his ghost powers makes for exciting race moments.
One interesting plot twist could be that Danny's friends initially don't recognize him as Dan Phantom and try to befriend him, not realizing the danger. Another could be that Dan Phantom has some hidden memories of his time as Danny that start to resurface at crucial moments, changing his evil intentions.
Sam is also quite popular. Her goth - like personality and her strong - willed nature make her an interesting character. In fanfiction, she can be portrayed in different ways, like being even more involved in Danny's ghost - fighting activities.
Obviously, the main character would be Danny Phantom himself, but in two different forms or versions. One would be the original Danny Phantom from the canon source, and the other would be a version created by the fanfiction. There might also be his friends like Sam and Tucker who could play important roles in helping the two Dannys understand each other and deal with any issues that arise from their meeting.
In addition to the ghosts, there might be some human characters that are important in the 'phantom city danny phantom fanfiction'. They could be Danny's friends or family members who get involved in the events of the Phantom City. Their reactions to the supernatural world and their interactions with Danny and the ghosts would add an interesting dynamic to the story.