Gohan will most likely encounter other Z - fighters like Krillin and Tien. They were all part of the group back then. Also, there's a good chance he'll meet Master Roshi. Roshi was a key figure in Goku's training, so his interaction with Gohan could be really interesting. He might also come across Bulma, who was always involved in the Dragon Ball story, either by accident or because he needs her help with some time - related technology or something.
In this fanfiction, Gohan could meet characters that he never got to interact with properly in the original timeline. For instance, he might meet Bardock, Goku's father. This could be a very emotional and important encounter as Gohan would be able to learn more about his family's history from Bardock directly. He could also meet some of the villains from the past in a different context. Maybe he'll encounter King Piccolo and try to change the way things went down in their previous battles. And who knows, he might even meet some minor characters from the past that had a small but significant role in the overall story and end up changing their fates.
In this fanfiction, Gohan might change important events in the past. For example, he could prevent certain villains from getting stronger or save characters who died previously.
I think Captain America would be a likely ally. Captain America is all about justice and doing what's right, which aligns well with Gohan's values. They both have a strong moral compass and would respect each other's fighting abilities.
Perhaps the biggest plot twist would be if Future Gohan's time - traveling somehow connects to a greater cosmic force or an ancient prophecy. His journey back in time could be part of a larger plan that he wasn't aware of. This could introduce new enemies or allies that are related to this cosmic plan. It might also mean that his actions in the past are not just about saving his own future, but about saving the entire universe from a much greater threat that was yet to be revealed.
Goku is often a common character. Since Gohan has a strong relationship with his father, in time - travel scenarios, they might interact a lot. For example, Gohan could go back in time to save Goku from an early death or to train with him. Vegeta is also a likely character. He might be skeptical of Gohan's time - traveling at first but then get involved in Gohan's plans. Another common character would be Piccolo. He has been Gohan's mentor, and in time - travel stories, he could offer his wisdom and help to Gohan again.
Cell could be a great antagonist. Even if Gohan goes back in time, Cell might still find a way to exist. Maybe he adapts his plan to absorb the Androids earlier in time. Gohan would then have to face a more powerful and unpredictable Cell, who could potentially change the timeline to his own advantage.
Cell - like characters are often antagonists. Since Cell was such a major foe in the original series, new versions of Cell - like beings could be created in fanfiction to make Gohan angry. They might target his loved ones or the Earth itself, provoking Gohan's rage.
The main characters are bound to be Bardock and Gohan. Bardock with his fierce Saiyan warrior past and Gohan, who has his own unique blend of Saiyan and human qualities. There might also be other supporting characters like Piccolo who could pop in to add some more depth to the story, or perhaps even Bulma if she has some role to play in the time - travel or dimension - hopping aspect of the story.
Well, perhaps Gohan goes back in time to save his father, Goku, from some early danger. He could then train alongside Goku when they were younger, leading to a much stronger Goku earlier in the timeline. This could also have a ripple effect on the relationships within the Z - fighters. For example, with a stronger Goku earlier, their battles against the Red Ribbon Army or other villains might be much easier and quicker.
One possible plot could be Gohan going back in time to the Saiyan saga. He could use his knowledge of future events to prevent certain tragedies. For example, he might try to save the Saiyans from Frieza's wrath. He could also train with the younger versions of Goku and the other Z - fighters, sharing his advanced techniques and knowledge, which would significantly change the power dynamics in the battles against the Saiyans and later enemies.
He could meet an old master from the past who has some unique training methods. This master might teach Gohan some long - forgotten Saiyan techniques.