Well, in many 'James Potter alive' fanfictions, his character development can take a different turn. Since he's alive, he may have a chance to grow in ways he didn't in the original. He could be more cautious, for one. In the books, he was quite bold and reckless at times. But in fanfic, coming back from the 'dead' might make him more aware of the risks. Also, his relationships can develop differently. He might form new friendships or strengthen old ones in ways that weren't possible before. For example, he could have a closer bond with Sirius, having realized how much he missed him during his 'absence'. And he could be more involved in the fight against the dark forces, using his experience and new - found wisdom in a different way than we expected from the original James Potter.
In some 'James Potter alive' fanfictions, his character can be more mature. For example, if he comes back after a long time, he might have learned from his past mistakes. In the original, we saw him as a bit of a troublemaker in his youth. But in fanfics, he could be more responsible, especially if he realizes he has a second chance to be a better father to Harry or a better friend to his mates. He might also be more empathetic, having seen the consequences of his actions (or rather, his 'death') on those he left behind.
Often, fanfic authors give Cho a more complex backstory. Maybe she has family secrets related to the wizarding world's history. This can lead to her making different choices. For instance, she could be more involved in the Order of Phoenix's activities earlier on, rather than just being on the sidelines as in the original. This new backstory can also affect her relationships with other characters, like her friendship with Hermione or her rivalry with Ginny in a more nuanced way.
Well, in some fanfictions where Naruto is a fox, his character can be more in tune with his animal instincts. He might be more cunning and quick - thinking, using his fox - like abilities to his advantage in battles. For example, he could use his enhanced senses to detect hidden enemies or traps more easily.
His backstory could be explored in more depth. We could see more details about his time after winning the Hunger Games and how it led to his state in the 75th Hunger Games. Maybe he had some untold experiences that made him more cynical or more determined, which would be different from what we know in the original series.
In fanfiction, Harry might be more worldly. Since he gets more exposure to Viktor and Durmstrang, he could pick up on different magical traditions faster. For example, he might start using some Bulgarian hexes in his duels. Viktor, on the other hand, could be shown to be more open - minded. In the books, he was a bit reserved. In fanfiction, he could be more eager to learn about Hogwarts' ways and make more friends there.
Some characters might develop new skills. For instance, Hermione could learn a type of magic from another universe that makes her even more powerful. This would change her role in the story and how others interact with her.
Well, in fanfiction, Severus' character can be developed to show his softer side towards Lily earlier on. In the books, we mainly see his tough exterior and his actions as a double agent. But in fanfiction, we might see him expressing his love for Lily in more open and desperate ways. As for Lily, she could be developed in a way that she is more empathetic towards Severus' situation. In the books, she seemed to cut him off quite harshly, but in fanfiction, she might try to understand his reasons for getting involved with the Death Eaters and still hold some hope for their relationship.
In some fanfictions, Podrick's character might be developed to be more assertive. Instead of being the quiet and obedient squire, he could take charge in certain situations. For example, he could be the one to make decisions during a dangerous journey.
He would be more confident. Without the trauma of losing his parents, Harry would not have that underlying sense of insecurity. He would probably be more outgoing and less hesitant in making friends and taking risks.
He could be more brooding. Since Pluto is associated with the Underworld, Percy could have a darker, more introspective side. He might spend a lot of time thinking about the nature of death and the afterlife.
The way Fem Luke interacts with the Force could also be different. Maybe she has a more intuitive connection to the Force, especially when it comes to aspects like sensing the emotions of others. This could make her a more empathetic Jedi, and it could also change how she uses the Force in combat or in diplomatic situations. For example, she might be able to defuse tense situations by sensing the underlying emotions of the parties involved and using the Force to soothe them.