One idea could be that the OC is a powerful warrior from a different dimension. They meet Kefla during a universal tournament. Their powers are so different yet complementary that they start to train together, and gradually a deep bond forms between them as they learn from each other's fighting styles.
Some dedicated Dragon Ball fan communities on social media platforms might also be a good source. For example, certain groups on Facebook or Reddit where fans discuss and share their fanfiction works. However, the availability of exactly this pairing might vary. You may need to do some searching within those communities.
It gives a chance for creativity in exploring gender - swapped or alternate versions of the characters. Fanfiction writers can play with the personalities and backstories of these characters in ways that the original series might not have explored. For example, they can write about how the female Vegito might approach a relationship with Gogeta differently than a male Vegito would, adding new layers to the story.
Create a unique backstory for your OC. Give them a motivation and a history that ties into the Dragon Ball universe in an interesting way. For example, if your OC has a vendetta against a certain villain that Kefla has also faced, it can create an instant connection between them.
First, know the characters well. Understand their individual powers, personalities, and backstories. This will help you create believable interactions between them. For example, Vegito might be more serious and calculated, while female Gogeta could be more impulsive and energetic. Second, come up with an engaging plot. It could be a battle - centered story or a more character - driven one about their relationship development. Third, use vivid descriptions to bring the story to life, especially when they are in combat or having an important conversation.
A possible plot could be set in a world where the Saiyan population is on the verge of extinction again. Female Gogeta and Vegito are the last hope. They are initially hesitant to work together as they have different ideas on how to save the Saiyans. But during their journey, they encounter various obstacles that require their combined strength. Through shared experiences like saving a group of innocent Saiyan children, they start to see each other in a new light and their relationship evolves into a strong partnership.
One aspect of Vegito and Female Gogeta fanfiction could be the exploration of their unique power combinations. In these fanfictions, writers might create scenarios where they team up against a powerful enemy. For example, they could face a new, extremely strong villain that neither could defeat alone. Their combined strength and different fighting styles would make for an exciting story.
If Vegito never unfused, it might mean that the enemies he faced were simply not strong enough to force the separation. This could imply that the story's difficulty level was lower than originally thought. Or, it could be that some external factor prevented the unfusing, creating a whole new set of plot twists and complications.
A common theme is power escalation. Writers often make them even more powerful than in the original series, creating epic battles. For instance, they might face off against multiple foes at once, showing off their enhanced abilities.
One popular Gogeta and Vegito fanfiction might be those that explore their power levels in new and creative ways. For example, a story could have them facing an extremely powerful new enemy that forces them to combine their powers in unexpected ways.