Who might be the main characters in 'Phineas and Ferb Ferb Gets Sick' fanfiction other than Phineas and Ferb?

Well, it could be about how Phineas tries his best to take care of Ferb. Maybe he builds some crazy contraption to make Ferb feel better, like a super - advanced bed that can do all sorts of things to ease Ferb's illness.

Well, Mom would be very concerned. She would drop whatever she was doing and take care of Phineas. She might make some of her special home remedies to help with the diarrhea. Dad, on the other hand, would try to be the joker and make Phineas laugh to take his mind off the discomfort. And Doofenshmirtz, if he somehow gets wind of this, might try to use it as an opportunity to create a new -inator to stop the boys' fun, but in the end, it could backfire on him as he realizes it's not a good thing to take advantage of a sick kid.

Definitely Doofenshmirtz. He could mess with one of Phineas and Ferb's inventions in a way that really ticks Phineas off. Like he might use one of his -inator devices to turn their amazing flying machine into a pile of junk. Phineas would be furious and would then set out to fix it and get revenge on Doofenshmirtz.

Doofenshmirtz could be the antagonist. He might create a contraption that directly or indirectly causes Phineas to get mad. For example, his -inator could accidentally zap away all of Phineas's blueprints for his latest project. Phineas would be understandably angry and would then see Doofenshmirtz as the source of his frustration.

Well, perhaps in the fanfiction, Phineas gets mad because Ferb accidentally ruins one of their big inventions. Maybe they were building a huge roller coaster and Ferb made a miscalculation that made the whole thing collapse. Phineas, who is usually calm and positive, gets really frustrated and yells at Ferb for the first time.

Maybe not. It could be a fan - created story that has gained some popularity, but not an official part of the franchise.

Perhaps Phineas gets diarrhea right before a big event they were planning, like a huge backyard invention showcase. This causes chaos as they have to delay the event. Meanwhile, Candace, thinking this is a perfect opportunity to get the boys in trouble, tries to call their mom. But Ferb manages to keep her at bay while also taking care of Phineas.

One possible plot could be that Phineas gets dysentery right in the middle of one of his big summer projects. His friends and family then have to figure out how to take care of him while still trying to keep their daily adventures going. Ferb might take on more of the leadership role in their projects while also looking after his brother.

One possible plot could be that someone ruins Phineas's big invention project. Maybe Doofenshmirtz creates a device that accidentally targets Phineas's backyard and destroys all the materials for his amazing new roller coaster. This makes Phineas really mad and he decides to go on a mission to get back at Doofenshmirtz. Ferb tries to calm him down but Phineas is too angry at first. Then they end up working together to not only fix their project but also teach Doofenshmirtz a lesson about being more careful with his inventions.

Well, Phineas and Ferb are the central characters. They are brothers with very creative minds. In the 'Scary Story', they are likely to be the ones driving the plot forward, whether they are exploring a spooky place or facing some kind of mystery. Their sister Candace might also be involved. She often tries to bust her brothers' activities, and in a scary story setting, she could add some comical relief or even be part of the overall spooky adventure.