It could be about the Egyptian gods reacting to the modern interpretations and creative twists in the fanfiction. Maybe they find the new characterizations of themselves amusing or offensive.
The plot might also center around the gods using the fanfiction as a way to understand modern human perception of them. They could be comparing the fanfiction's version of their powers and personalities to the traditional ones. They might also be looking for any hidden meanings or messages that the fanfiction writer is trying to convey about them and their place in the modern world.
Ra would be a likely candidate. He's one of the most important Egyptian gods, and his reaction to the fanfiction would be interesting. He might be offended if his power is misrepresented or amused if the writer has come up with a unique take on his role.
You can try some fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions including those related to 'The Red Pyramid'. Just search for 'The Red Pyramid' on the site, and you'll likely find many fanfictions to read.
Well, perhaps Naruto could be transported to the world where Pyramid Head exists. He might initially be confused and scared as it's a very different environment from his own. He could then use his ninja skills to try and figure out what Pyramid Head is and how to deal with it. Maybe he tries to fight it at first, but realizes that Pyramid Head is not an ordinary enemy and has to use his wits more than his strength.
One highly recommended 'The Red Pyramid' fanfiction is 'The New Adventures of Carter and Sadie' on AO3. It continues the story in an exciting way, exploring new magical elements and character developments.
One idea could be Percy having to team up with an Egyptian demigod to stop a common enemy that is causing chaos in both Greek and Egyptian mythological realms. Maybe a powerful monster that is using the powers of both mythologies to grow stronger.
Set, the Egyptian god of chaos. He could be a great antagonist as he might see the combination of Greek and Egyptian powers in Percy and the other demigods as a threat to his own plans of spreading chaos. He could try to manipulate events to turn the two groups against each other.
When Carter and Sadie read The Red Pyramid fanfiction, it could be a mixed bag. Some fanfictions might stay true to the original lore and add more depth to their relationship as siblings and magicians. Others could take a more creative turn and put them in completely different scenarios, like a modern - day high school setting while still having their magical powers. This can be both strange and fascinating for them.
Perhaps the Jackal Army is in search of a powerful artifact that was lost long ago. Naruto, with his skills in finding hidden things and his ability to overcome obstacles, joins them on their quest. Along the way, they face many challenges like traps in ancient tombs and battles with other mythical creatures. Naruto uses his shadow clones to solve some of the puzzles and his Rasengan to fight off enemies. The Jackal Army, on the other hand, uses their knowledge of Egyptian magic and their physical strength. As they get closer to the artifact, they realize that there is a greater conspiracy at play that involves a powerful ninja from Naruto's world who wants to use the artifact for his own evil purposes.
The fanfiction might involve Percy being a guide for an Egyptian god who is new to the mortal world. Percy shows the god how things work in this world, and they get into all sorts of adventures together. For example, they could be trying to stop a dark force that is threatening to disrupt the balance between the mortal and divine realms. And during this journey, the Egyptian god might use his unique powers and Percy his own skills to overcome the obstacles.
It could be about the Roman gods' reactions to the events in 'The Last Olympian'. Maybe they are amused, or they might have different opinions on how the Greek gods handled things.