In this fanfiction, a possible plot twist is that when Lucy travels back in time, she meets a version of herself that is much more powerful and has a completely different personality. This other Lucy has been living in the past and has made different choices, which has led to a very different life. They have to either work together or compete with each other. It could also be that the time travel was not accidental but was actually set up by someone in the future who has their own motives for sending Lucy back, and she has to figure out who and why.
One interesting plot twist could be that when Lucy goes back in time, she discovers that her family has a much darker secret than she ever knew. Maybe they were involved in some sort of magic that was considered forbidden in the past. Another could be that she accidentally changes the future in a way she didn't expect, like making her friends not become the people she knew them as. And perhaps she finds out that an enemy in the present was actually once an ally in the past, and she has to figure out what went wrong to turn them into an enemy.
Well, a cool plot twist might be that Lucy goes back in time and realizes that she was the cause of a major event that she had always thought was just a part of history. For example, she might find out that a great magical disaster was her fault because of something she did when she first traveled back. Also, she could discover that the magic she uses in the present was actually created by her in the past, but she has no memory of it. It would really mess with her understanding of herself and her magic.
Well, obviously she'll interact with her past self. It would be really interesting to see how she reacts to seeing a younger and more naive version of herself. She could also meet characters who are no longer alive in the present. For example, if there were any great wizards from the past who played important roles in the history of magic. Additionally, she might cross paths with some of the villains from the past who were causing trouble long before the current villains in the story. This could change her perspective on the whole conflict in the present.
One interesting plot twist could be that Thor goes back in time and accidentally changes something that makes him lose his powers. For example, he might prevent the event that led to him getting Mjolnir, and then has to find a new way to be a hero without his trusty hammer. Another could be that he goes back and meets a younger version of Loki who doesn't yet hate him, and he has to figure out how to keep it that way so that their relationship in the future is different.
Maybe he goes back in time and meets a younger version of his enemy. Instead of fighting right away, he tries to understand what made the enemy turn bad in the first place. This changes the whole future dynamic between them when he returns to his own time. He might find out that there was a misunderstanding that led to all the hatred.
One interesting plot twist could be that Naruto, with his knowledge of the future, tries to prevent certain tragedies but ends up causing new ones. For example, he might try to save a character too early and disrupt the natural flow of events, leading to unforeseen consequences.
A cool plot twist might be that Fem Harry goes back in time and discovers that her parents were involved in a secret mission that was never revealed before. This could lead to her having to deal with the consequences of uncovering that truth. Also, she could find out that Voldemort had a different origin or a hidden weakness that was lost in history. As she tries to use this knowledge to defeat him earlier, she might face opposition from some of the older wizards who don't believe her or are afraid of the changes she could bring. It could also be that she changes the way magic is taught at Hogwarts, introducing new spells or techniques from the future that create a whole new set of challenges and opportunities for the students.
Well, it could be that Lucy goes back to a time when Lula was in a difficult situation and she uses her modern knowledge to help Lula out. Maybe she helps Lula with some sort of social issue or a personal problem that was prevalent in that time.
One common plot twist could be that Naruko discovers she has the power to change not only her own fate but also the fate of the entire village. For example, she might prevent a major disaster that originally happened in the past. Another could be that she finds out a hidden truth about her family or a powerful jutsu that was lost in time. Maybe she realizes that a person she thought was an enemy in the present was actually a friend in the past and has to figure out how to reconcile that in the future.
Well, sometimes in these fanfictions, a plot twist might be that Sirius goes back in time and discovers a hidden truth about his family. Maybe he finds out that there was a secret alliance or a hidden enemy within the Black family that was influencing events all along. This could completely change his perception of his family's past and his place in it. Also, he could go back in time and end up being involved in a different kind of magic that was lost in his original time, like an ancient form of magic that has the power to either save or destroy the wizarding world.
One possible plot twist could be that when they go back in time, they accidentally change something that has a huge impact on their future relationships. For example, Naruto might unknowingly prevent Sasuke from leaving the village in the past, which could completely change how they interact in the present they return to. Another could be that they find out a hidden truth about their parents or the village's past that was covered up, like a secret alliance that their predecessors were involved in.
One possible plot could be that Naruto is somehow transported to the Fairy Tail world where he meets Lucy Heartfilia. They could team up to fight a common enemy that threatens both their worlds. Naruto's unique ninja skills combined with Lucy's celestial spirit magic would make for some epic battles.