Perhaps he meets a version of his parents who are still alive. This would be an incredibly emotional encounter for Harry. He would get to know them, and they could teach him things about magic and life that he never had the chance to learn before.
He might meet different versions of his friends. For example, a Hermione who is a powerful sorceress ruling a magical kingdom. It would be exciting as he could learn new magic from her and be part of her adventures in this alternate reality.
First, come up with a unique concept for your alternate universe. It could be something like a world where ninjas use modern technology. Then, think about how the characters will be different. For Naruto, maybe he's not an orphan or he has different abilities. Next, plan out the plot. You can start with a small change in the Naruto universe and build on it. For instance, if the Uchiha clan was never massacred, how would that change the relationships and the overall story?
One great 'alternate universe naruto fanfiction' is 'Road to Ninja: Naruto the Movie - Another Side'. It presents a very different Naruto world where characters have different personalities and roles. For example, Naruto has a family in this AU which changes his whole dynamic.
Well, Hermione is often depicted in different ways in these fanfics. In some alternate universes, she could be a powerful dark witch instead of the studious and good - hearted character we know. Ron might be a super - confident and arrogant character rather than the sometimes insecure boy in the original story. Also, Snape could be a completely different person. He could be a jolly and friendly teacher rather than the brooding and complex one we are used to.
In some 'Harry Potter travels to alternate universe fanfic' plotlines, Harry might find that his parents are alive in the alternate universe. This would be a huge emotional rollercoaster for him. He would have to deal with the fact that he has a different family dynamic, and also figure out how this affects the fight against evil. Additionally, the alternate Hogwarts could have different teachers or even different subjects. This would open up a whole new world of exploration for Harry.
In this fanfiction scenario, Naruto could bring his ninja skills to the Def universe. He'd probably have to adapt to the new environment. For example, if the Def universe has different laws of physics, his usual jutsu might not work the same way. He might also learn new techniques from the Def universe and combine them with his own.
Well, in some 'naruto goes to alternate universe fanfiction' plots, Naruto might find himself in a world where all the ninja clans have merged into one big super - clan. He'd have to navigate the complex politics within this new structure. Also, there could be a plot where he enters an alternate universe where the Fourth Great Ninja War never happened, but there are new threats emerging that he has to face. And then there's the idea of a universe where Naruto's parents are alive, and he has to deal with a completely different family dynamic.
In Naruko fanfiction, one interesting concept could be a world where Naruko has a different set of ninja skills. For example, she might master a unique form of water jutsu that no one in the original Naruto universe has seen before. Another concept could be her relationships being completely different. Maybe she forms a strong bond with characters who were antagonists in the original story, like Orochimaru, but in this alternate universe, he has a different, more positive role to play. Also, the idea of Naruko leading a different ninja team with members from different villages could make for an exciting plot.