Perhaps the plot involves Percy helping Apollo with a secret mission. Since Percy is good at handling tough situations, he could be assisting Apollo in retrieving a lost artifact. They keep their friendship a secret because Apollo doesn't want the other gods to think he's relying too much on a demigod.
It could be Hades. He might not like the idea of Percy, a son of Poseidon, being friends with Apollo. Hades could see it as a threat to his own power or plans in the underworld.
One possible scenario could be Percy teaching Apollo and Artemis about modern mortal world. Percy could introduce them to things like skateboarding. Apollo would be excited and eager to try, while Artemis might be more reserved but still curious. They could bond over these new experiences and their shared sense of adventure.
A possible storyline is that there is a prophecy about the end of the world which can only be averted if Percy and Apollo work together in a very specific way. They have to find a set of ancient artifacts that are scattered across different realms. Along the journey, they argue and learn more about each other's personalities, but in the end, they manage to fulfill the prophecy and save the world, strengthening their bond as best friends.
Well, it could be about Percy and Apollo becoming friends in an unexpected way. Like, Apollo is in a situation where he loses his godly powers temporarily and Percy helps him out. During this time, they bond over their shared experiences of being different from regular humans. They start to understand each other's strengths and weaknesses, and form a strong friendship.
They could go on a quest together. For example, to retrieve a powerful artifact that has been lost in a dangerous realm. Percy's ability to navigate through tricky terrains, Apollo's gift of light and prophecy to guide them, and Artemis's hunting skills to protect them from lurking threats would all come in handy. It would be a great way for them to bond and learn about each other's strengths.
Another common theme is adventure. Percy is usually involved in some sort of adventure, and his secret friends play a crucial role in it. They might help him defeat a powerful enemy, or find a hidden treasure. For example, in one fanfiction, Percy and his secret friends embark on a journey to find a lost magical artifact that has the power to save their world from an impending doom. The story is filled with action - packed scenes and the bond between Percy and his friends grows stronger as they face difficulties together.
It could be an old enemy of the gods, like Kronos. Even though he was defeated before, he could find a way to come back and target Percy and Apollo specifically. Since Percy has been a thorn in the side of many of the Titans' plans before, and Apollo is a powerful god, Kronos might see them as a threat to his new - found or potential power.
One great Apollo and Percy fanfiction is 'Apollo's Adventure with Percy'. It has an interesting plot where Apollo and Percy team up to face a new threat in the demigod world. The story is full of action and their interactions are really well - written.
One interesting aspect of Percy, son of Apollo fanfiction could be his relationships. He might have unique interactions with other demigods. For example, his bond with those from different cabins could lead to exciting adventures. Maybe he teams up with a child of Athena to solve a mystery that involves both Apollo's powers of prophecy and Athena's wisdom.