One idea could be that the OC is a new gem who arrives on Earth and Lapis is initially suspicious but gradually warms up to them as they show their kind nature. For example, the OC might help Lapis with her water powers, like finding new ways to control and shape water in a more creative way.
The OC could be a gem hybrid, part of a new type of gem created by accident. Lapis meets this OC who is struggling to fit in both in the gem world and on Earth. Lapis, having her own experiences of being different and out of place, decides to take the OC under her wing. They could go on adventures together, like exploring uncharted parts of the ocean on Earth or hidden gem ruins. As they do so, their relationship develops from friendship to something more romantic.
One interesting story could be about Lapis Lazuli and Steven going on an adventure together to discover a new gem colony. In this fanfiction, they might face various challenges that test their friendship and understanding of each other.
A more emotional plot could be an OC who was once part of the Homeworld gems but defected. They have a lot of guilt and self - doubt because of their past actions. In the fanfiction, they try to make amends by helping the Crystal Gems. But they constantly fear that their old allies will come after them. This internal struggle and their journey of redemption could be a really interesting story.
Well, the OC could be a human - gem hybrid. This would make them an outcast in both human and gem society at first. But as the story progresses, some of the main characters like Pearl, Amethyst, and Peridot start to form a bond with the OC. Maybe they are all intrigued by the OC's dual nature and the way they navigate between the two worlds. This could lead to a harem - like situation where they all have different relationships with the OC, some more platonic, some with a hint of romance.
Maybe a time - travel plot where Steven, Peridot, Lapis, and Lemon are sent back to a crucial moment in Gem history. They have to work together to make sure the events unfold in a way that doesn't disrupt the present. Along the way, they learn more about each other's pasts and grow closer as a group.
Perhaps Steven finds himself in a situation where he has to protect a number of characters, and in the process, they all fall for him. Like he could be on a mission to save some of the corrupted Gems, and as he heals them, they see his pure intentions and are drawn to him. This could lead to a harem where they all vie for his attention in different ways, some being more shy and others more bold in their affections.
Start with their appearance. Decide if they have a unique gem placement or color that sets them apart. For example, if they're a new type of gem, maybe their gem is a different shape. Then, think about their personality. Are they shy like Lapis was at first? Or are they outgoing and adventurous? Their backstory is also crucial. Maybe they were created for a special purpose but that purpose was lost over time. This could lead to them having a sense of being lost which Lapis can relate to.
A plot could involve a half - gem OC who is half Emerald and half Peridot. The OC is discovered by a group of rogue gems who want to use her unique powers for their own gain. She has to escape from them and find her way to the Crystal Gems. Along the way, she discovers that she has the ability to create energy shields like an Emerald and hack into technology like a Peridot. Another idea is a half - gem OC half Topaz and half Bismuth. She is born during a time of peace but when a new war breaks out between Homeworld and the Crystal Gems, she has to decide which side to fight for, as she has qualities from both sides.
Yes, there are likely fanfictions out there that might feature a kiss between Steven and Lapis. The Steven Universe fandom is quite creative, and fans often explore different relationship dynamics in their fan - made stories. However, the official show may not have such a scenario, but fanfiction allows for all kinds of interpretations and romantic pairings that deviate from the main plot.
Another idea is a human OC who is a detective in Beach City. They start to notice strange happenings that are related to Gem activity. As they dig deeper, they get involved with the Crystal Gems and become an ally. They could use their detective skills to help the Gems solve mysteries, like finding missing Gem shards or uncovering the secrets of an ancient Gem structure.
Maybe the giant OC is a guardian of a long - lost power. The story could revolve around Steven and the gang trying to figure out how to communicate with this giant, who seems to be protecting something important. It could lead to adventures where they have to learn the giant's language and culture, which is very different from their own.