Well, it could be that the other dimension has a time - warp. Naruto enters and finds that he is in the past or future of his own world. If it's the past, he might accidentally change things that could have a huge impact on his own dimension. In this new dimension, there could also be a different form of the tailed beasts. Maybe they are combined into one super - powerful beast. Naruto's encounter with this new form could be a major plot twist as he tries to figure out how to deal with it, either befriend it or fight it.
One possible plot twist could be that in the other dimension, Naruto finds out that all his friends have different personalities. For example, Sasuke could be a peaceful scholar instead of a brooding avenger. Another twist might be that the chakra system works completely differently in this new dimension. Maybe instead of using hand signs, they use some kind of mental power to perform jutsus. Also, Naruto could discover that the Akatsuki in this dimension are actually the good guys, fighting against an evil ninja clan that wants to take over the world.
Well, perhaps Natsu could find himself in a dimension where magic works completely differently. He might have to learn new ways to use his fire magic or even discover new types of magic altogether. Maybe he meets alternate versions of his friends who have different personalities due to the different environment of that dimension.
His relationship with Sasuke would be very different. In the new dimension, Sasuke might not have the same vendetta against his brother. So Naruto wouldn't have to worry about Sasuke going off the rails. With Sakura, she could be a powerful ninja in a different way, like she might be more focused on medical ninjutsu and Naruto would see her in a new light. And his relationship with Kakashi could change too. Maybe Kakashi is a strict military - like leader in the other dimension instead of a laid - back teacher.
One exciting plot twist could be Octavia traveling back in time and accidentally changing a key event that led to the creation of the Ark. This would completely rewrite the history of the 100. Another could be her meeting a younger version of herself and trying to guide her without revealing her true identity. It would create a lot of internal conflict for Octavia as she sees her younger, more naive self.
A plot twist could be that Sakura travels back in time and realizes that the world she thought she knew was all a lie. The history books in her time were wrong. She could find that the origin of her magical powers was something very different from what she was taught. Also, she might go back to a time when there was a powerful artifact that was lost in her own time. However, when she tries to retrieve it, she discovers that it has a dark side that she didn't expect. This could lead to a moral dilemma for her, whether to keep it or leave it be.
Well, a really interesting plot twist in an Eren travels back in time fanfiction could be related to relationships. Say Eren goes back and realizes that his actions in the past have a huge impact on his relationships with his friends. Maybe he accidentally causes Mikasa to not be as attached to him as she was in the original timeline. Or he could find out that Armin was supposed to be the one with the time - traveling ability all along, and his interference messes up Armin's future plans. Also, what if he goes back and discovers that the real enemy wasn't the Titans but some other force that was using the Titans as a distraction, and his time - traveling journey is the only way to expose this truth.
Naruto's character develops in many ways. Firstly, he becomes more adaptable as he faces different situations in each dimension. He has to quickly figure out the rules and powers in each new place. Secondly, his understanding of power grows. In some dimensions, his Rinnegan - based abilities might be limited, so he has to rely on his wits and other skills, which makes him more well - rounded. Thirdly, his sense of empathy deepens. Meeting different beings in various dimensions, some of whom might be suffering, makes him more determined to protect and help those in need, just like he does in his own world.
He might face different types of chakra and powers that he's not used to. In a new dimension, the laws of nature regarding ninjutsu could be completely different. For example, his Shadow Clone Jutsu might not work as effectively if the chakra in that dimension behaves in an unexpected way. Also, he could encounter new and strange creatures that have abilities he has never seen before, making it difficult for him to fight or even communicate with them.
One interesting plot twist could be that Minato travels back to a time when the Hidden Leaf Village is on the verge of a civil war. He uses his future knowledge to prevent it, changing the entire future of the village. Another could be that he travels to a time where his parents are still alive and has to deal with the complex emotions of seeing them again.
One common plot twist could be that the end, when traveling back in time, accidentally changes something that has a huge ripple effect on the future. For example, they might prevent an important event from happening that was crucial for the development of a certain technology or the rise of a key character. Another plot twist could be that the end realizes they are not actually in their own past but in an alternate timeline. This can lead to a whole new set of challenges as they try to figure out how to get back to their own timeline or if they should even try to change things in this new one.
One interesting plot twist could be that when Tom Riddle travels to the future, he discovers that his name has become a symbol of great evil, and he has to face the consequences of the actions his future self took. This forces him to re - evaluate his own path and potentially change for the better.