One interesting idea could be the origin of the ectoplasm baby. Maybe it was created accidentally by Danny during one of his ghost - fighting adventures. Another idea could be the baby having unique powers that are a mix of Danny's ghost powers and something new related to the ectoplasm. For example, it could have the ability to manipulate ectoplasm in ways Danny can't.
I'm not sure of specific 'Danny Phantom ectoplasm baby' fanfiction off the top of my head. But you can try searching on fanfiction websites like Archive of Our Own or FanFiction.net. They usually have a wide variety of Danny Phantom fanfictions that might include something related to ectoplasm and baby themes.
Well, for Danny Phantom baby fanfiction, you could write about Danny having to babysit a baby that has the ability to see ghosts like he does. It would be full of comical moments as Danny tries to keep the baby calm while also dealing with ghosts. Or perhaps a story where Danny discovers a baby ghost in the Ghost Zone and decides to bring it back to the human world to protect it. You could also write a story where Danny's parents find a baby with strange energy readings and Danny has to keep his identity a secret while trying to figure out what's going on with the baby.
One idea could be that Danny's ghost powers somehow lead to an unexpected pregnancy situation for a female character, and then he has to deal with the responsibilities of being a 'baby daddy' while still keeping his ghost - fighting a secret. For example, maybe a new ghostly enemy targets the unborn child.
One plot idea could be that baby Danny accidentally wanders into Vlad's lair. Vlad, instead of being his usual villainous self, is surprisingly gentle. He realizes that Danny's innocence might be a chance for him to change his ways. Maybe he tries to mentor Danny in a different, more positive way, teaching him about his ghost powers in a non - malicious manner.
A plot could be that a magical spell gone wrong makes Sam and Danny age down to babies. Tucker discovers that there's a time limit to reverse the spell. Meanwhile, the two babies are exploring the world in a very different way, seeing things from a new perspective. This could lead to some heartwarming and funny interactions with their families and friends as they all try to solve the mystery of the spell.
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.
One idea could be exploring Danny's relationships in a different way. For example, how his friendship with Sam and Tucker might develop if they faced a new supernatural threat. Another could be a story where Danny discovers a new power and has to learn to control it while dealing with school and his ghost - fighting duties. And perhaps a fanfiction where Danny travels to an alternate dimension within the Danny Phantom universe.
A great fanfiction idea could be a time - travel story within the Danny Phantom Phantom Planet universe. Danny somehow gets sent back in time to before he became a half - ghost. He has to figure out how to get back to his own time while also dealing with the knowledge he has of the future. This could lead to some really interesting interactions with his past self, his family, and friends. And he might accidentally change things in the past that could have a huge impact on the future of the Phantom Planet.
One idea could be that Danny discovers a new ghostly power that he uses to take revenge on a group of bullies who have been tormenting his friends. He could use his intangibility in a creative way, like sneaking into their lockers and making their things disappear.
One idea could be Danny Fenton having to deal with a new ghostly enemy that can manipulate time, making his double life as Danny Phantom even more chaotic. Another could be Danny trying to balance his high school life, including exams and relationships, while also facing a ghost invasion that only he as Danny Phantom can stop. Or perhaps a story where Danny Phantom discovers a hidden power within himself that has a connection to his human side, Danny Fenton.