Vegeta would be a great character to include. His rivalry with Goku could add some interesting dynamics in the crossover. Also, Piccolo, with his strategic mind and powerful attacks, could be useful in facing the new challenges. And if it's a crossover into another anime universe, someone like Naruto could be included. Naruto's never - give - up attitude and his own set of powerful jutsu could create some amazing team - up moments with Goku.
Definitely include Bulma. She could be the one to provide some technological support or even figure out the mechanics of the crossover. Another good character would be Trunks. His sword - fighting skills and his half - Saiyan powers could be a great addition. If it's a crossover into a DC universe, Superman could be in it. The contrast between Goku's ki - based powers and Superman's superhuman abilities would make for some exciting battles and interactions.
One possible plot could be Goku from the SSJ4 form crossing over into the world of Dragon Ball GT. He could encounter new threats that require his ultimate form to defeat. Maybe he teams up with the other Z - fighters in that universe to face off against a powerful and ancient evil that was sealed away long ago and has now been unleashed.
Hermione Granger from 'Harry Potter' could be an interesting addition. She could use her magic knowledge to study the mummy. Maybe she could find a spell to control or at least understand the mummy better. It would be a really unique combination of magic and ancient Egyptian mystery.
Professor Oak could also be an interesting addition. As a Pokémon expert, he might be fascinated by Mewtwo and try to study it. This could create a conflict as Mewtwo is not one to be easily studied. It could also lead to a deeper understanding of Mewtwo's origin and abilities.
Batman would be a great character to include. His no - kill rule contrasts with Deadshot's assassin nature. Their interactions would be full of tension and moral debates. Harley Quinn could also be included. Her chaotic personality could add an element of unpredictability to the story. She might team up with Deadshot for a mission or be a distraction during one of his hits.
Vegeta would be a great choice. Their rivalry in the original Dragon Ball series could be taken to a whole new level in a crossover setting. Another good character could be Trunks. Since Goku Black has a connection to Trunks in the main story, it would be interesting to see how they interact in a different scenario.
Definitely Superman. The Man of Steel's powers are somewhat similar to a Saiyan's in terms of strength and flight. It would be interesting to see how Goku's daughter and Superman interact. Also, Spider - Man could be a good choice. His quick - wittedness and acrobatic skills combined with her raw power would make for an engaging story.
For a crossover with a classic cartoon like Tom and Jerry, Jerry could be a really interesting character to include. Jerry is always getting into scrapes with Tom. Maybe Doc McStuffins could be the one to treat Jerry's little bumps and bruises after his run - ins with Tom. And she could also try to make Tom understand that he shouldn't be so rough with Jerry.
In a 'baki the grappler crossover fanfiction', characters like Kenshiro from 'Fist of the North Star' would be great. His powerful martial arts skills would contrast well with Baki's grappling. Also, Goku from 'Dragon Ball' with his superhuman strength and energy attacks. And Naruto from 'Naruto' with his ninja skills and large - scale jutsu could create interesting interactions with Baki.
The Teenage Mutant Ninja Turtles would be great. Leonardo, Donatello, Michelangelo, and Raphael could meet Kick and teach him some new fighting moves. In return, Kick could show them some crazy skateboarding tricks. They could all team up to fight a new villain in New York City.
Another character that could be included is Lara Croft from 'Tomb Raider'. She's an expert in exploring ancient tombs and dealing with ancient curses. She could join forces with the characters from 'The Mummy 2017' to stop the mummy. Her athleticism and knowledge of ancient artifacts could be very useful in the fight against the mummy.