Some fanfictions feature Eren time traveling to different points in the history of the Titans. He might go back to the origin of the Titans to understand how they came to be. By doing this, he hopes to find a way to end the Titan curse once and for all. This often leads to him having to interact with ancient Titan shifters and uncover long - lost secrets.
One common theme is redemption. For example, they might go back in time to correct past mistakes either in their own actions or in the events related to the fight against Titans. Another theme is the exploration of their relationship. Time travel can be a tool to show how their relationship could have developed differently under different circumstances. For instance, in some fanfictions, they may have met earlier in a different time period and their initial interactions are quite different from the original story.
Time travel in fanfiction often forces Eren to face his own limitations. He realizes that even with the power to time travel, he can't always control everything. This realization humbles him and makes him more empathetic. He starts to understand the complexity of the world and the fact that every action has far - reaching consequences. As a result, his character becomes more complex and well - rounded.
One popular 'eren jaeger x levi time travel fanfiction' is 'Through Time and Titans'. It has an interesting plot where Eren and Levi are sent back in time and have to deal with their past selves while also trying to change the future of the world against the Titans. Another one could be 'Time's Twist' which focuses more on the emotional journey of Eren and Levi as they travel through different time periods and how their relationship evolves during these travels.
One common theme is identity. Since Eren is female in these fanfictions, there's often exploration of how she fits into the world that was originally designed around a male Eren. Another theme is relationships, like her friendships or potential romances with other characters in a different light.
One common plot twist is that the kidnappers turn out to be people Eren thought he could trust. For example, in some fanfics, it could be someone from his own military unit who has a hidden agenda. This adds a layer of betrayal and makes the story more complex.
I'm not sure if it's extremely popular. Fanfiction often combines different universes in unique ways, but this particular combination might be a niche idea. It depends on the overlap between Harry Potter and Attack on Titan fandoms.
One popular plot could be Ichigo traveling back in time to prevent a major event in the Soul Society's history that had a negative impact. For example, he might go back to stop Aizen's early machinations. Another plot could involve Ichigo traveling forward in time to see the future of his friends and the world he's protecting. He could then come back to the present and work towards a better future. There could also be a plot where Ichigo time travels to different alternate universes where things are very different for him and his friends, like in one universe he never became a Soul Reaper and has to figure out how to get back to his own reality.
One popular 'female Eren Jaeger fanfiction' is 'The Female Titan's Secret'. It explores an alternate storyline where Eren is a female and has different relationships with other characters. Another great one could be 'Female Eren: A New Perspective' which delves into how her being female changes the overall narrative of the original story.
One popular plot is when Sasuke and Naruto accidentally get sent back to their academy days. This gives them a chance to correct misunderstandings from the start and perhaps form a closer bond earlier. Another plot could be that Naruto travels forward in time and sees a future where Sasuke has gone down a dark path, and he has to go back to change things.
Often, a strong female character is a key element. She may have her own goals and motives that interact with Eren's journey. For example, she could be on a mission to save her family and crosses paths with Eren.