Perhaps Luke goes back in time and realizes that the events that led to the fall of the Jedi Order were not as straightforward as he thought. He could discover that there were other forces at work, not just the Sith. This new knowledge could make him question everything he knew about the Jedi and their history. He might also find that his family had a different role in the past than he was aware of, which could change his perception of his own identity and purpose. When he returns to his own time, he could use this new understanding to reshape the Jedi Order in a more informed and effective way.
A plot twist might be that when Luke goes back in time, he finds out that the Force has a different set of rules in the past. This could lead to him having to relearn how to use the Force in this new 'historical' context. He could also meet characters that were thought to be long dead in his time, and these characters could either be allies or enemies. For instance, he might encounter an ancient Sith Lord who was thought to be only a legend. This would create a whole new set of challenges for Luke as he tries to find his way back to his own time while dealing with this unexpected threat.
Well, perhaps a plot twist could be that when Kirito goes back in time, he discovers that his own existence in the past was a key factor in creating the problems he faced in the future. So, he has to figure out a way to change things without erasing himself. Or, he could go back and find that the person he loves in his original timeline has a completely different personality or role in the past, which throws him off and makes his feelings really complicated.
One possible plot twist could be that when they go back in time, they accidentally change a small event that has huge consequences in the present. For example, they might prevent a meeting between two people that was crucial for the formation of a powerful coven, and now they have to figure out how to fix it before they return to their own time.
One possible plot twist could be that Dark Naruto tries to change the past to prevent his own dark transformation. He might attempt to save someone important who in the original timeline led him down the dark path. For example, if it was the death of a certain character that made him turn dark, he could go back and try to save that person. This would completely change the future and the Naruto we know from the original story.
Another plot twist could be that the magic in the Harry Potter universe is actually a precursor to the Force. Harry Potter discovers that his magic has the potential to evolve into the Force - like powers. This revelation makes him question his place in the wizarding world and whether he should pursue a different path, one that is more in line with what Luke Skywalker represents in the Star Wars universe.
One possible plotline could be that Luke and Leia go back in time to prevent the rise of the Empire. They might try to stop key events like the corruption of Anakin Skywalker. For example, they could warn the Jedi Council about Palpatine's true nature. Another plotline could be that they go back to save their mother. They would have to figure out how to do this without changing too much of the future. Maybe they'd work with young Obi - Wan Kenobi.
A plot twist could be that they end up in the wrong time period completely. Instead of the time they intended to go to, they land in a much earlier era of magic. There, they discover secrets about magic that have been long forgotten in their time. However, they also face the danger of getting stuck there because the magic that sent them back was calibrated for a different time, and they have to find a way to adapt it to return home.
One possible plot could be that Luke is lured by the power the dark side offers. Maybe he gets frustrated with the slow progress of the light side in bringing order to the galaxy. He might see the Sith as more efficient in getting things done. For example, if the Republic is still facing numerous threats and the Jedi are tied by their code not to take extreme measures, Luke could be tempted to cross over.
A possible plot twist is that Kakashi goes back in time and finds out that the events he thought were true in the past were actually misinformation. This could completely change his perception of the history of the ninja world and his own role in it. Also, he might go back to a time when Orochimaru was just starting his dark experiments. Kakashi could try to stop Orochimaru right from the start, but in doing so, he might end up creating new villains or problems. Or perhaps, when he travels back, he loses some of his memories from the future, which makes it difficult for him to use his knowledge effectively to change things.
A great plot twist could be that Darth Vader travels back to the time when the Jedi Order was at its peak. His dark side presence is detected by the Jedi Council immediately. However, instead of being able to simply capture or kill him, they find that his knowledge of future events gives him an edge. He might use this to manipulate the Jedi, creating internal strife within the Order. This could also lead to some Jedi being tempted by the dark side because of the power that Vader represents. And all of this could ultimately reshape the future of the galaxy far more than anyone expected.
A great plot twist could be related to the time - travel itself. What if the way time - travel works in the WW2 era is different from how it is in Harry's time? This could lead to him getting stuck or being unable to use his magic properly. Or perhaps he discovers that a certain event in WW2 was actually caused by a wizard from the future (not just him) who was trying to correct something in the wizarding world's past. His attempts to fix things could then make the situation even more complicated as he unknowingly steps on the toes of a much larger time - traveling plan.