I'm not that familiar with the specific 'Brian Piccolo Thanksgiving Day story'. Maybe it could be about how he spent the Thanksgiving Day with his family, sharing a big meal and giving thanks. It might also involve some special traditions he had on that day.
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.
There were a few novels that fit this description, such as Legend of the Earth Emperor, Mountain God in the City, Incense Becomes God, I Actually Became a Mountain God, and so on. You can choose one according to the plot introduction of these novels and your own taste. I wish you a happy reading!