Definitely Nico di Angelo. He has his own mysterious ways and powers. He could be a key figure in uncovering the truth behind Percy being framed. Maybe he has some underworld connections that help in the investigation. Another character would be Tyson. Percy's half - brother is strong and kind - hearted. He could be used as a sort of protector for Percy when he's on the run or being wrongly accused. Also, Chiron. As the camp's mentor, he could play a role in either believing or doubting Percy at first, but eventually helping him in the end.
Percy is, of course, the main focus. However, in many of these fanfictions, Luke Castellan can also be a major character. Since Luke had his own issues with the gods and turned to the dark side in the original series, he could either be an influence on Percy's dark turn or an ally in his new dark journey. Nico di Angelo is another character who could be involved. Given his connection to the Underworld and his own complex relationship with Percy, he might try to understand what's going on with Percy or try to fight against him if he thinks Percy has gone too far.
Percy Jackson himself is obviously a main character. His struggle with bloodlust is often the central focus. Annabeth Chase also frequently appears as she tries to help Percy deal with his issues, using her intelligence and strategic thinking.
Obviously, Percy Jackson himself is often the central character in such fanfictions. His friends like Annabeth Chase can also be involved. In some cases, she might be the one trying to keep Percy out of trouble or, on the contrary, joining him in his 'delinquent' adventures. Grover could also be there, perhaps reluctantly getting dragged into Percy's misadventures.
Percy Jackson himself is often the main character. He has a connection to the sea, and in pet fanfiction, he might find a sea - related pet like a hippocampus that he befriends and trains. Annabeth Chase could also be involved. She's smart and might use her knowledge to help with any problems the pet causes or gets into.
Percy Jackson himself is often involved. He might be given a bow in some fanfictions and have to adapt his combat style to include archery. Annabeth Chase could also be involved as she is very intelligent and could strategize around the use of bows in battles. Another popular character is Nico di Angelo. His dark powers could be combined with the use of a bow in an interesting way in fanfiction, like his arrows having some sort of shadowy effect.
Percy Jackson himself is often involved. He might encounter the wolf in the woods around Camp Half - Blood and have to figure out if it's a friend or foe. Another common character is Annabeth. She could use her wisdom to analyze the significance of the wolf in the context of the Percy Jackson lore.
Grover can play a role too. Although he is Percy's best friend, in some fanfictions, there could be a situation where Percy gets jealous if Grover spends more time with Annabeth on a quest or if Grover seems to have a closer bond with her in a particular situation. It's not as common as Percy - Annabeth or Percy - Nico scenarios, but it can add an interesting twist to the fanfiction.
In these types of fanfictions, Nico di Angelo could play a significant role. Given his connection to the underworld, he might be involved in trying to either retrieve Percy's soul or deal with the after - effects of his death. Also, Luke Castellan's spirit could make an appearance, maybe taunting Percy in his final moments or having some role in the events leading up to his death.
Grover could be there too. He might be the one who first discovers Percy is being bullied and tries to cheer him up or find a way to stop it. And of course, there could be the bullies, who might be mortal kids at first, but later could be revealed to have some sort of connection to the mythological world, like being descendants of minor monsters or something.
The gods would be involved. Zeus, Poseidon, or any of the other gods. If they make decisions that affect Percy negatively, like sending him on a dangerous mission without proper support, he'd be angry. Also, Clarisse could be in these stories. She and Percy have had their share of conflicts in the original series, and in a fanfic, she could do something to really tick Percy off, like stealing his thunder (figuratively speaking) in a battle or competition.