They might name him after a Greek hero, like Theseus. It has a strong and heroic sound to it, fitting for a child of Percy and Annabeth who are both very heroic themselves.
How about 'The Three Heroes'? This name showcases that there are three important members in the band, all of whom can be considered heroes in their own right. They have all had their own heroic adventures in the fanfiction, so it would be a great name to represent them as a band.
I don't know for sure as I haven't read this particular fanfiction, but usually in fanfiction, Percy could be a character from a popular book, movie or TV series.
I'm not sure who Percy specifically is without reading the fanfiction. It could be an original character created by the author, or perhaps a reimagined version of a known character from a particular franchise that the fanfiction is based on.
Percy in 'percy sings fanfic' could be a local singer or an amateur performer who decided to take on the interesting task of singing fanfic. Maybe it's a stage name, or it could be someone within a small community of fans who is known for this unique activity. Without more context, it's difficult to say for sure who this Percy is.
Past Percy is likely to be more impulsive. He hasn't faced as many challenges yet and might act before thinking. Future Percy, on the other hand, would be more cautious and calculating, having learned from past experiences.
In Percy tired fanfiction, Percy often shows signs of physical exhaustion. His usual energetic actions might be slower, like his sword - fighting skills not being as sharp. For example, in some fics, he might stumble during a fight instead of his usual confident moves.
Well, in many fanfics, Percy might be depicted as having a conflicted relationship with bloodbending. He could be shown as initially reluctant to use such a powerful and somewhat dark ability.