Then, introduce some shared experiences. Maybe they get trapped in a strange dimension together. In this new and dangerous place, they have to rely on each other's strengths. Goku's physical power and Frieza's cunning could be the keys to their survival. As they go through these experiences, they start to see each other in a new light and their relationship begins to change.
Well, friendship is also a theme. Despite their differences, they might form an unlikely friendship. In some fanfictions, they learn from each other. Goku might learn about strategy from Fem Frieza, while Fem Frieza could learn about determination and the will to protect from Goku. And of course, adventure is a big theme. They could go on quests together, exploring new planets and facing new challenges.
One common theme is redemption. Frieza is often portrayed as having a chance at redemption through his interactions with Goku. For example, in some fanfics, Goku's unwavering belief in the good in people (or in Frieza's case, beings) starts to make Frieza question his own evil ways.
In some lemon fanfiction, their interaction can be filled with tension. Goku, being the good - natured Saiyan, may be initially wary of Frieza. But as the story progresses, they might find common ground. For example, they could start to respect each other's power.
In fanfiction, the unique aspect of Goku and 18 is their contrasting natures. Goku is a Saiyan, full of energy, always eager for a fight, and has a somewhat innocent view of the world. 18, on the other hand, is an android, created with a more cynical view due to her origin. Their interactions can be really interesting as they bridge these two different outlooks. For example, Goku's positive attitude might start to change 18's more negative perspective over time.
One possible fanfic could be about Goku's intense training before the Cell Games. He might be shown pushing his limits in the Hyperbolic Time Chamber, trying out new techniques and forms to defeat Cell. Maybe he discovers a new power level that no one, including himself, expected.
Sure. There are fanfictions that show Goku and Videl in different scenarios. For example, some might have them training together in a new way that we haven't seen in the original series. These stories often add more depth to their characters and their relationship. You can find some great ones by reading reviews and ratings on fanfiction platforms.