The older characters such as Kakashi would be cautious. They would recognize Naruto but also be worried about the implications of someone from the future being in the present. They would want to know if his presence could change the future in a negative way. For example, they might fear that his actions could lead to the earlier awakening of a powerful enemy. As for the villains, they might see future Naruto as a threat and try to eliminate him as soon as possible. Orochimaru, for instance, would be very interested in Naruto's future powers and might try to capture him to study. And the new generation of ninja in the past would look up to future Naruto, seeing him as a symbol of what they could become.
In a 'Dbz Goku meets Bardock' fanfiction, it could start with Bardock somehow being brought back to life or time - traveling to Goku's era. They might initially have a bit of a clash because of their different upbringings. Goku was raised on Earth with love and kindness, while Bardock grew up in the harsh Saiyan society. But as they get to know each other, they find common ground. Bardock could be in awe of Goku's Super Saiyan transformations and Goku could be eager to learn about his Saiyan roots from his father. They could also form a strong bond and work together to protect the universe from new threats.
One interesting story could be about Black Goku's origin in a different universe where his transformation into an evil Saiyan had a more complex backstory involving a corrupted wish on the Dragon Balls. It might explore how his actions in that universe led to him crossing over into the main Dragon Ball Z universe.
The fanfic could tell a story of the Future Warrior teaching the Dragon Fist to a new generation of fighters. He would have to pass on not only the physical technique but also the mental discipline required to use it effectively. This could involve stories of his own experiences and how he overcame difficulties to master the Dragon Fist.
The comic might involve characters going back in time to face old challenges or change events. Maybe they aim to prevent a disaster or meet past versions of themselves.
Some DBZ characters might be confused by the out - of - canon scenarios in Death Battle fanfiction. For example, Goku, being a pure - hearted fighter, might be a bit puzzled by some of the more extreme or uncharacteristic match - ups in the fanfiction.
Goku could develop a deeper sense of his Saiyan identity. Knowing his father, he might start to embrace more of the Saiyan warrior spirit. Bardock might change too, seeing the good in the universe through Goku's eyes.
One interesting fanfiction could be where Bulma and Goku have to team up to save the world in a unique way that wasn't shown in the original series. Maybe they have to travel to a different dimension together and face new enemies.
Well, obviously Black Goku himself is a main character. He is the center of the story in most cases as his actions drive the plot. Goku also features prominently as he is the one who has to oppose Black Goku. Vegeta is often there too, as he is another strong Saiyan and is eager to take on the threat that Black Goku poses.