One idea could be Goku ending up in the DC universe and having a friendly spar with Superman. Their different power sources and fighting styles would make for an exciting encounter. Maybe Goku learns about Kryptonite and how it affects Superman, which gives him a new perspective on weaknesses.
Another plot could be Goku getting caught in the middle of a battle between Batman and Joker in Gotham City. Goku, with his pure - hearted nature, tries to understand Batman's no - kill rule and at the same time, figures out how to deal with the Joker's chaotic and unpredictable behavior. This could lead to some really interesting character interactions as Goku tries to bring some peace to Gotham in his own way.
A great plot could involve Goku teaming up with the Flash. Goku's teleportation - like Instant Transmission and the Flash's super - speed would be a really cool combination. They could race across the DC universe to stop a powerful villain who is trying to steal all the speed force. And along the way, they could learn from each other's abilities and training methods.
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.
One idea could be Goku Black crossing over into a modern-day Earth where he has to deal with advanced technology that he doesn't understand at first. Another could be a crossover with a different anime universe, like Naruto, where Goku Black's power clashes with the ninja abilities. Maybe he teams up with Naruto against a common enemy.
One idea could be Goku from Dragon Ball crossing over into a world like Fairy Tail and having a harem of the female mages there. Maybe he helps them in battles and gradually forms relationships with them.
Another plot could involve Xeno Goku getting stranded in a different anime world during the crossover. He has to adapt to the new rules and powers there while also trying to find a way back home. He could make new friends and enemies in this strange world.
One idea could be that Goku and Vegeta are transported to an alternate universe where they have to team up with their alternate selves to defeat a powerful new enemy that is a combination of all the foes they've ever faced. This would force them to not only work together but also understand different versions of themselves.
One idea could be Goku crossing over into a different anime universe, like the Naruto world. He could end up in a fight tournament there and show off his Super Saiyan Blue form. His ki attacks would be a new and strange concept to the Naruto characters.
One idea could be that Goku is transported to a different universe where he meets various female characters from different anime. They are all intrigued by his power and his pure-hearted nature, and a harem dynamic starts to form as they all want to be around him and train with him.
One idea could be a tournament where Goku and Naruto are both invited. They start off as rivals but then realize they have more in common as they face powerful opponents together. Another could be a situation where an enemy from Goku's universe somehow ends up in Naruto's world and they have to team up to defeat it. A third idea is that a magic spell or some kind of power - related accident causes their powers to be swapped, leading to comical and also challenging situations as they try to adapt to each other's abilities.
Another plot could involve Gohan being mistaken for a new metahuman in the DC universe. As he tries to find his way back home, he gets caught up in a conflict between the Justice League and a group of supervillains. His Saiyan powers could be the key to resolving the situation.
One idea could be Wolverine getting transported to the DC universe and teaming up with Batman. They could combine their detective skills to solve a mystery that involves both mutants and metahumans. For example, a new villain is creating chaos in Gotham by using some sort of technology that affects Wolverine's healing factor in strange ways.