To write this kind of fanfic, start with a strong hook. Maybe start with Steven waking up in the Underground or Frisk arriving on Earth near Beach City. Then, build the story gradually. Show how the characters react to the new environment and each other. Don't forget to add some action and conflict. It could be a battle between the Gems and some of the more aggressive monsters from Undertale. And make sure to stay true to the essence of both universes. Don't change the core personalities of the characters too much. This way, fans of both shows will be able to enjoy your fanfic.
A possible Undertale and Steven Universe crossover fanfic could be really interesting. It might involve characters from both universes meeting in a strange new world. For example, Steven could end up in the Underground from Undertale. He would probably try to use his powers of peace and love to resolve conflicts there, like how he does in his own show. Maybe he'd meet Sans and Papyrus, and there could be some really funny interactions. Sans with his laid - back attitude and Steven's positive energy would make for a great comical duo.
One interesting storyline could be where Steven's gem powers interact with the magic in the Undertale world. For example, his ability to heal might have a unique effect on the monsters in Undertale. Maybe he could heal some of the more damaged monsters and in turn, they help him understand their world better. Another could be a story where the characters from both universes team up to face a common threat. The Sans and Papyrus from Undertale could join forces with Steven and the Crystal Gems to fight against a powerful enemy that is a threat to both their worlds. It would be really cool to see how their different fighting styles and powers work together.
In a Steven Universe and Undertale crossover fanfiction, the characters' personalities would blend in some fascinating ways. Steven's open - mindedness would allow him to accept the strange and wonderful aspects of the Undertale world without much hesitation. His friendly nature would make him approachable to all the characters there. Ruby and Sapphire, who make up Garnet, have very different personalities. Ruby's hot - headedness and Sapphire's calmness could create some interesting interactions. In Undertale, characters like Undyne, who is very passionate about her beliefs, might either clash or find common ground with Ruby. Meanwhile, Sapphire's ability to foresee possible futures could be a very valuable asset in the unpredictable world of Undertale, and she could use it to help the group make better decisions.
Another possibility is that a Marvel hero, say Spider - Man, accidentally ends up in Beach City. He teams up with Steven to deal with a local threat that is also related to some sort of interdimensional chaos. For example, a group of villains from the Gem world and the Marvel world are working together to open portals to other dimensions to steal valuable resources. Steven and Spider - Man would have to use their unique abilities to stop them.
A common concept is the character interactions in steven universe crossover fanfic. Writers often like to see how Steven would get along with characters from different shows. For instance, if there was a crossover with My Little Pony, Steven might have interesting conversations with Twilight Sparkle about magic and friendship. Some fanfics also focus on the world - building aspect, like how the Gem world would merge with the world of another show in a crossover.
One common theme is the exploration of different cultures. In both Steven Universe and Homestuck, there are unique cultures. In crossovers, it's interesting to see how the Crystal Gems' way of life and values interact with the trolls' or the kids' in Homestuck. For example, the idea of friendship and loyalty is strong in Steven Universe, and it can be contrasted or combined with the relationships in Homestuck.
One possible plot could be that Dipper and Mabel visit Beach City while on a road trip. They meet Steven and the Gems. The Mystery Shack's oddities could interact with Gem magic in strange ways. For example, a Gem artifact might be mistaken for a regular Mystery Shack item and cause chaos when activated.
A plot could involve a powerful villain that threatens both the Naruto universe and the Steven Universe. So, Naruto and Steven have to team up. Steven could use his healing powers on Naruto's friends who get injured in battles, and Naruto could use his Rasengan to break through tough defenses of the enemy. They could also exchange their beliefs and values. Naruto could teach Steven about perseverance and never giving up, while Steven could show Naruto the power of love and acceptance in a more in - depth way.
Pearl would be an interesting character to include. Her grace and combat skills, combined with her complex backstory, could add depth to any crossover. In a crossover with a historical - themed show, Pearl's knowledge of different eras could create interesting storylines. Another interesting character is Garnet. Her fusion status and stoic nature can lead to unique interactions, especially in a crossover with a show that also has characters with dual identities or special powers.