He might become more cautious. Since the future is unknown and full of new things, he would have to be careful. For instance, he can't just rush into a fight without knowing what his opponents are capable of.
His sense of humor could change. The future might have different kinds of jokes or ways of being funny. He could pick up on some of these new comedic styles. Also, if he meets different types of people in the future, he might adjust his humor to fit in better. Maybe he starts making references to future pop culture or technology in his jokes, which would be really strange for his friends back in his own time.
His personality might become more reserved. As a Cullen, he'd have to fit into their more subdued lifestyle. He might lose some of his brashness.
When Percy is made a god in fanfiction, his personality could shift towards being more authoritative. He has to deal with other gods and manage his own domain. So he might become less impulsive as he now has more at stake. His kindness towards mortals could either increase as he has more power to protect them, or decrease as he becomes more involved in godly affairs. His confidence would likely soar, but it could also turn into arrogance if he's not careful.
His personality would likely experience a shift towards a more solemn and responsible demeanor. With godly powers come great responsibilities. Percy would no longer be able to act as carelessly as he did as a demigod. He might become more reserved in showing his emotions, especially as he realizes that his actions as a god can have far - reaching consequences. Also, his loyalty might be tested as he has to balance his new divine status with his relationships from his mortal days.
He might encounter advanced technology that he has no idea how to use. For example, flying cars or holographic communication devices. It would be really funny to see him struggle with these new things at first.
If Percy joins the Volturi in fanfiction, his personality could change in multiple ways. At first, he might be very resistant to their ways. But as time passes, he could become more like them in some aspects. He would be surrounded by vampires who are mainly concerned with power and control. This could make him more power - hungry. But also, Percy has a strong sense of justice. So, he might try to use the Volturi's power structure to enforce his own sense of right and wrong. This could lead to him being more authoritarian in his approach. He might also become more isolated as he can't fully trust the other Volturi members, which could make him more withdrawn and less likely to show his true emotions.
He might become more aloof. As a goddess, he'd be in a different social strata than before. He'd be more removed from the daily struggles of demigods and mortals, which could make him seem less approachable.
Well, Percy's personality transformation would be complex if he becomes a wolf. He might become more in tune with the natural order. His sense of loyalty could intensify, much like how wolves are loyal to their pack. This could mean that he becomes even more protective of his friends, seeing them as part of his 'pack'. On the other hand, his communication style could change. Instead of relying on words, he might use more body language and growls to convey his feelings. And his relationship with authority might also shift. He could be more resistant to being ordered around, as wolves have their own hierarchy and he might see himself as an alpha in some situations. This new personality would add a whole new layer of depth to his character in the fanfiction.
Percy Jackson's personality could change quite a bit in another world in fanfiction. His sense of humor might be affected as the new world may not have the same cultural references that he's used to in his own world. He could become more solitary as he tries to figure out this new place on his own. However, his underlying sense of justice would likely remain. He would still be drawn to help those in need, but he might go about it in different ways. He might also develop a new sense of pride in being able to adapt and survive in this new world, which could change how he presents himself to others.
He might become more aloof. Being a god often comes with a sense of superiority, but Percy has always been down - to - earth. However, his new status could make him a bit more distant from his mortal friends at first. But deep down, he'd still be the same Percy with a strong sense of right and wrong.
He might become more aloof. Since Chaos is such a vast and unpredictable concept, Percy may start to distance himself from his old, more emotional self. He could become more calculating as he has to deal with the new and often dangerous situations in the chaos realm.