Another idea is that the villains from both universes team up. Orochimaru from Naruto and one of the Gem Homeworld villains might join forces. This would force the heroes from both shows, like Naruto and the Crystal Gems, to work together to defeat this new and powerful threat. They would have to learn about each other's strengths and weaknesses really fast in order to succeed.
In some fanfics, there could be a situation where Steven visits the Naruto world. He might be really confused at first by all the ninja stuff. But then he could start to use his Gem powers in creative ways to help out. He could heal injured ninjas with his healing spit, and the ninjas would be amazed at this strange power from another world.
One interesting crossover could be Naruto characters in the world of Steven Universe. For example, Naruto's ability to use chakra could be a unique power in the SU universe. Maybe he could use his Shadow Clone Jutsu to help out in a gem battle. Another could be Steven trying to understand Naruto's ninja way and learning some of his moves to defend Beach City in a new way.
A really interesting crossover is when the Gem technology and Naruto's jutsu are combined. For instance, the Gems' ability to teleport could be compared to some space - time ninjutsu. It's fascinating to see how the two different power systems interact.
Another possibility is a crossover with "Gravity Falls". Dipper and Mabel could come to Beach City during a mystery involving Gem technology. Their knowledge of the strange and unusual from Gravity Falls could combine with Steven's understanding of Gem lore to solve the mystery.
When the Star Wars spaceships visit the world of Steven Universe. Just imagine the Millennium Falcon landing in Beach City. The reactions of the local characters like Steven and his friends would be hilarious. And the pilots from Star Wars would be equally amazed by the strange and beautiful world of Steven Universe.
One interesting crossover could be the use of magic in the Steven Universe world. For example, Steven might learn some basic spells from the Harry Potter universe and use them in his own world to solve problems in a new way. Maybe he could use a levitation spell to move the big rocks around on the beach more easily.
One creative crossover could be Ben using his alien forms in the world of Steven Universe. For example, Heatblast could help with some of the gem - related heat - based problems. Another could be Steven's healing powers affecting Ben's aliens in a unique way, like speeding up their recovery if they get injured during a fight. And perhaps the Omnitrix could interact strangely with the gem technology, leading to new power combinations.
In these fanfics, we get to see our favorite characters from both series in new situations. For example, Naruto might befriend Steven and learn about the power of love and acceptance from him. Or the Gems could be intrigued by Naruto's chakra and want to study it. These crossovers allow for a lot of character development and interesting interactions.
One interesting crossover could be the characters from Gravity Falls and Steven Universe teaming up to solve a mystery that involves both the Gem world and the strange happenings in Gravity Falls. For example, Dipper and Steven might combine their knowledge of the supernatural to figure out a new threat.
In Steven Universe and Dragon Ball Z fanfiction, there could be epic battles. Picture Steven and the Crystal Gems teaming up with Goku and his friends against a common enemy. The different fighting styles would make for an exciting story. Also, the concept of fusion in both series could be explored further. What if a character from Steven Universe fused with a Dragon Ball Z character? It would create a whole new and powerful being with a blend of their unique traits.
One interesting Steven Universe fanfic could be about the Gems exploring a new planet and encountering unique creatures. It might focus on how they interact and learn from these new beings.