Well, he could end up in a situation where he has to team up with his past - self. This would be really interesting as they would have different levels of power and knowledge. His past - self might be confused by his presence, and they could have some comical misunderstandings while trying to figure out how to get Goten back to his own time.
In fanfiction, if Goten travels to the past, he may encounter old villains who were thought to be defeated. These villains could see Goten as an opportunity to change their fate. Goten, on the other hand, would have to use his skills and knowledge from the future to either defeat them again or find a new way to deal with them, all while trying not to disrupt the past too much.
He might accidentally change the future. For example, he could prevent important events from occurring that were crucial for the development of the present he came from. Maybe he meets his parents at a younger age and reveals too much about the future, which could cause them to make different decisions.
Well, in a fanfiction where Naruto travels to the past, he could meet his parents when they were young. He could also learn new jutsu from the past ninjas that were lost over time. Maybe he'd even be able to influence the early development of the Hidden Leaf Village in ways that would make it stronger in his own time.
Goten could meet the younger versions of his friends like Krillin or Yamcha. They might be a bit skeptical of him at first. He could also run into Master Roshi, who would probably be interested in Goten's abilities and might try to teach him some old - school techniques. And there's a chance he meets Bulma, who could be intrigued by his futuristic knowledge and might even try to get some tech ideas from him.
She could change the future of the Cullen family. Maybe she stops a certain event from happening that would have led to their downfall in the original timeline.
Well, in such a fanfiction, it might be that Gohan's class is about martial arts. Goten shows up, and they end up having a friendly sparring session during the class. This could be a great opportunity to show how Goten has grown in his skills and how Gohan has developed as a teacher. Maybe the other students in the class would be in awe of Goten's natural talent.
In such a fanfiction, Naruto might try to prevent some of the tragedies that occurred in the past. For example, he could stop the Uchiha massacre. He would use his knowledge from the future to change things. Maybe he'd also be able to save some characters who died early in the original story, like Jiraiya. And he could potentially have a huge impact on the relationships between different clans, as he'd know about future conflicts.
Well, they might change some major events. For example, they could prevent a big battle that had a lot of casualties in the original timeline. Maybe they'd help their parents at a younger age, giving them an edge in fights. They could also introduce new techniques to the past, which would change the power balance among the Z - fighters.
One possibility is that Ichigo could try to change certain events in his past. For example, he might want to prevent a tragedy that occurred or give himself some advice that would make his journey easier. He could also end up causing more chaos if he interferes too much, as small changes in the past can have big consequences in the future.
In a fanfiction where Percy Jackson travels to the past, he might try to prevent some of the tragedies that occurred in the past. For example, he could attempt to stop the first Titan War from starting. He might use his skills and knowledge from the present to change the course of history, but this could also have unforeseen consequences, like disrupting the timeline and creating alternate universes.
She could experience the historical events of 1918 first - hand. It was a time of great change. There were things like the end of World War I and the start of the Spanish Flu pandemic. Bella would be in the middle of all that chaos or transformation.
In such a fanfiction, Goku might be seen as a very powerful and strange visitor in Konoha. He could start by showing off his amazing strength and speed during a training session with the ninja. Maybe he'd accidentally break some training equipment and leave everyone in awe.