Another possibility is a crossover with the Star Wars universe. Goku could land on a planet in the Star Wars galaxy. His Ultra Instinct might be seen as some sort of mysterious Force ability. He could get involved in the fight between the Jedi and the Sith. Maybe he would train with the Jedi to learn more about their use of the Force while also showing them his own unique martial arts skills.
One idea could be a crossover with the Naruto universe. Goku with his Ultra Instinct could face off against Naruto in his strongest form. They might start as rivals but then realize they have a common enemy and team up. The story could explore how their different fighting styles and powers interact.
A crossover with the DC Universe would be exciting. Imagine Ultra Instinct Goku going up against Superman. It would be a battle of strength, speed, and different power sources. Goku's Ultra Instinct, which gives him incredible reflexes and power, against Superman's Kryptonian abilities. The fanfiction could also involve other DC characters like Batman trying to figure out Goku's powers.
Maybe Goku gets mixed up in the events of the Injustice storyline. He could initially be confused by the alternate version of Superman who has gone bad. Goku, with his pure heart and Ultra Instinct, might try to bring the corrupted Superman back to the light. This could lead to some intense battles with the Injustice League as Goku tries to set things right.
Well, with Ultra Instinct, Goku would be able to react extremely quickly to the DC heroes' powers. For instance, when facing Flash, who is super fast, Goku in Ultra Instinct might be able to match his speed or even anticipate his moves better. This could lead to a mutual respect between them as they test each other's limits.
A possible plot is a crossover with the Naruto universe. Goku in Ultra Instinct mode could be mistaken for some sort of super - powered ninja. He might end up training with the Hokage or getting involved in the Akatsuki's plans. Since his Ultra Instinct gives him such incredible reflexes and power, he could easily hold his own against the strongest ninjas like Naruto in his Six Paths Sage Mode or Sasuke with his Rinnegan. It would be a clash of two very different power systems.
First, understand the characters well. Know Goku's Ultra Instinct powers, his personality, his goals. Then, when choosing a crossover universe, pick one that has elements that can contrast or complement Goku's world. For example, if it's a magic - based universe, how would Goku's physical powers interact with magic? Keep the story focused on the main characters and their development throughout the crossover.
Yes, it is possible. In fanfiction, writers have the creative freedom to reimagine the origin of characters. Goku being born with Ultra Instinct can add a whole new layer to his character development. It could mean that his power growth would be different from the original story, perhaps faster or with different challenges along the way.
You could write a fanfiction where Goku teaches others about Ultra Instinct. Maybe he tries to pass on this power to Gohan or Trunks. This would involve Goku having to understand the power more deeply himself in order to teach it, and it would also be a great way to develop the other characters.
One idea could be an Ultra Instinct Goku crossing over with the Dragon Ball Super universe and the Naruto universe. He could end up in Konoha and use his Ultra Instinct to sense and counter the attacks of the ninja there. Maybe he'd even have to fight some of the powerful ninjas like Naruto or Sasuke in a friendly sparring match to test their skills against his new form.
One possible plot could be that there is a rift in the multiverse that brings Goku and Luffy together in a strange new world. They initially misunderstand each other and start to fight. As the fight progresses, they both realize that there is a greater threat at hand that is causing the rift. So, they team up, with Goku teaching Luffy some of his combat techniques and Luffy showing Goku the value of friendship and loyalty in a different way.
A fanfiction could focus on Goku's relationships while in Ultra Instinct. For example, how does he interact with his friends and family? Does Vegeta view him differently? In this story, Goku might struggle to control the Ultra Instinct around his loved ones because it makes him seem so detached. This could lead to some interesting emotional moments between the characters.
Goku in Ultra Instinct mode is extremely powerful. He has superhuman speed, strength, and can dodge attacks effortlessly. However, Luffy also has his own set of amazing abilities like his Gear Fourth form which gives him enhanced speed and power. But I think Goku would win because his combat skills and power level are just on a different scale compared to Luffy.