One popular 'Danny Phantom Danny Dies' fanfiction might be 'The Aftermath'. In this type of fanfiction, the story often explores how the other characters deal with Danny's death. For example, Sam and Tucker may go through a period of extreme grief and guilt, wondering if they could have done something to prevent it. Another could be 'A World Without Danny', where the entire Amity Park starts to change in unexpected ways due to Danny's absence, showing how much of an impact he had on the town.
One possible storyline could be that Danny sacrifices himself to save the world from a powerful and evil ghost. Maybe he uses all his energy in a final battle and fades away, leaving his friends and family to mourn. Another could be that he's tricked by a villain into a death - trap that he can't escape from.
A new and powerful ghost that Danny has never faced before could be the main antagonist. This ghost could have unique powers that Danny isn't prepared for, and in their first encounter, it manages to defeat and kill Danny. This would set the stage for a story of revenge or trying to bring Danny back.
Often, they end on a bittersweet note. For example, the town may have finally found peace after Danny's sacrifice, but his friends and family are still mourning his loss. His friends might vow to carry on his mission in his memory, which gives a sense of hope among the sadness.
In this fanfiction, it could be that Danny Phantom meets a Danny Phantom from a parallel fan - made story. At first, they don't trust each other. But as they learn more about each other's worlds, they realize that there are some common elements that are being threatened. It could be that a powerful ghost is trying to rewrite all the fanfic universes related to Danny Phantom. So, they must combine their strengths and knowledge to stop this from happening.
Well, in this kind of fanfiction, Danny could be controlled by an ectoplasmic parasite. The parasite latches onto Danny and takes over his actions. His eyes might glow a different color to show he's not in control. His friends would first be confused, then realize something is amiss and start investigating.
Another possibility is that he's facing some emotional turmoil. Danny has a lot on his plate. He has to keep his identity a secret from his friends and family, deal with school, and fight ghosts. All this stress could be causing him to lose his appetite. He might be too worried or preoccupied to even think about food.
One possible story could be that Danny is facing a new and extremely powerful ghost. He needs help from his friends Tucker and Sam. Maybe they need to find a rare artifact to defeat this ghost. They could start by researching in the local library, looking through old ghost lore books. Tucker uses his tech skills to try and track down any leads on the artifact's location, while Sam uses her knowledge of the occult.
One idea could be that Danny gets an illness that affects his ghost powers. For example, he might start losing control over his intangibility or invisibility. This could lead to some really comical or dangerous situations. Another idea is that his friends try to find a cure for his strange ghost - related illness while also keeping it a secret from the town.
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.