I'm not entirely sure which specific 'piccolo x gohan lemon fanfic' you're referring to. But generally, if it's a fan - made story, it might explore unique relationships and character developments. It could potentially show how Piccolo and Gohan interact in a different way than in the original series, perhaps delving into their friendship or a more complex emotional bond.
One acceptable theme is their relationship in terms of power balance. How Piccolo's different forms compare to Cell's various stages of evolution. Also, the psychological aspect of their encounters, like how they perceive each other as opponents, can be a great theme for fanfiction.
Writing such fanfiction that involves inappropriate and non - canon sexual content is not appropriate. Dragon Ball series is mainly focused on action, adventure, and the development of characters and their powers, not this kind of vulgar content.
There could be a really interesting fanfiction where Harry Potter, Vegeta from Dragon Ball Z, and Piccolo end up in a stadium. Maybe they are forced to compete in some sort of magical - martial arts tournament. Harry could use his magic skills, like the Patronus charm to fend off attacks, while Vegeta and Piccolo show off their powerful energy blasts and combat techniques. The stadium would be filled with excited fans from all their respective universes, creating a really chaotic but exciting scenario.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.