A crossover could start with Steven somehow getting his hands on a piece of Voltron tech. This could be something that fell through a wormhole. His curious nature would lead him to try and figure out what it is. Meanwhile, the Paladins of Voltron are on a mission to retrieve this tech. When they arrive in Steven's world, they are shocked to find a world full of Gems. The two groups could then learn from each other's powers and ways of fighting.
A really interesting plot could be that a powerful Gem weapon is stolen and ends up in the Voltron universe. The Paladins find it and don't understand its power at first. Meanwhile, the Crystal Gems think the Paladins are the ones who stole it on purpose. So there's this initial conflict. But as they start to communicate, they realize there's a bigger threat behind the theft. A shadowy figure is trying to use the weapon to destroy both universes. So they must join forces to stop this threat. The story could explore how the different characters interact and grow to trust each other.
In the context of the show's universe, it's a bit of a strange concept. Since fanfiction exists in our real - world fandom and not in the show's world directly. But if we were to imagine a meta - situation where he could access it, I suppose it could be possible. However, it would be a very surreal situation for him.
Peridot is quite popular too. Her unique personality, especially her growth from a somewhat antagonist to a more friendly character, makes for great storytelling in crossovers. In a crossover with 'Ben 10', Peridot's technological knowledge could be paired with Ben's Omnitrix - related adventures.
Well, it could be really cool. Maybe the Gems would be intrigued by the technology of the Omnitrix. Steven might try to understand Ben's powers better and see if there are similarities between his gem powers and Ben's alien forms. And Ben could learn about the Gem culture. They could also exchange stories about their adventures and how they protect their respective universes.
To write a good Steven Universe FNAF crossover fanfiction, you need to consider the tone. Since Steven Universe is more light - hearted in general and FNAF is horror - based, find a balance. You could start with the Steven Universe characters in their normal setting and then gradually introduce the FNAF elements. Let the characters react realistically to the new and scary situation. For instance, Amethyst might initially be curious about the animatronics but then get scared when they start acting strangely.
It could be really interesting. Maybe the gems from Steven Universe end up in the spooky world of FNAF. They could use their powers to fight off the animatronics. For example, Garnet's strength could be used to hold the animatronics back while Pearl uses her spear to disable them.
Well, in such a crossover, Steven could use his gem powers to help the Avengers in battles. Maybe his healing powers could be used on the injured Avengers. For example, after a tough fight with a powerful villain like Thanos, Steven could heal Captain America's wounds.
First, know the characters well from both universes. For Steven Universe, understand the powers and personalities of the Crystal Gems and Steven. For Transformers, know the Autobots and Decepticons. Then, find a good starting point for the crossover, like an unexpected encounter. Don't forget to keep the tone consistent with both franchises.
It could be really cool. Imagine Steven's gem powers interacting with the Transformers' technology. Maybe the Crystal Gems could help the Autobots in some way, like using their powers to repair damaged parts. Or the Transformers could introduce new ways of using energy to the Gems.