Well, it could be about Broyl and Goku having to face various threats on Earth together. Maybe they start off as rivals but then realize they need to team up to defeat powerful villains. For example, they might encounter an alien race that wants to take over Earth. Their combined strength and different fighting styles could make for an exciting story.
In a Naruto fanfiction where Goku is sent to Earth, there are many possibilities. Goku's arrival could change the power balance completely. He could introduce new ways of fighting to the ninja world. For example, his Instant Transmission could be a game - changer in ninja battles. Also, his ability to constantly increase his power through training might inspire the ninja to train harder. His presence might also attract the attention of powerful enemies from other dimensions who sense his great power, leading to some epic multi - dimensional battles.
Well, Naruto would probably be super excited. He'd be looking around at all the new and different things on Earth compared to his own world. He might be amazed by the technology and the different kinds of people. And he'd surely want to show off his ninja skills while Goku would be there to protect him if any trouble came up.
It could be a powerful demon from another dimension. This demon could sense the power of Broyl and Goku and see them as a threat to his plans of universal domination. So, he decides to target Earth, where they are, to try and eliminate them.
Naruto could have all kinds of adventures. He might get involved in a fight against one of the Earth's villains, like Frieza if he somehow showed up. Naruto's Rasengan could be a powerful weapon against such foes. He could also explore different parts of the Earth, like the mountains or the oceans, which are very different from what he's used to in his own world.
Goku's powers would be a shock to the Naruto world. His super strength that can break mountains and his speed that is faster than the eye can see would make the ninjas reevaluate their own power levels. His powers would likely be the subject of much discussion among the ninja clans. Some might try to find ways to replicate his powers using chakra, while others would simply be content to have him on their side in battles against common enemies.