One idea could be exploring Adam's adventures in an alternate universe. Maybe in this universe, he has to team up with a different version of himself to save the day. Another could be delving into his relationship with his mother before the events of the movie in a more in - depth way.
A really interesting plot for 'the adam project fanfiction' would be to focus on the technology aspect. What if Adam finds an ancient piece of technology during one of his time - travels? This technology could hold the key to either saving the future or destroying it. He has to figure out how to use it, and in the process, he meets a group of scientists from a different time period who have their own ideas about the technology. This would lead to a lot of conflict and cooperation as they all try to understand and control the power of this mysterious technology.
One idea could be exploring what would happen if the main character had to go back in time one more time to fix an unforeseen consequence of his previous time - traveling adventures. Maybe he discovers a new villain who was created as a result of his actions.
One idea could be a story where the baby in the 'baby project' has some sort of special power that the characters have to figure out how to manage. Maybe the baby can communicate telepathically and it leads to all sorts of comical and heartwarming situations as the characters try to understand what the baby wants.
One idea could be Adam's backstory exploration. Maybe he had a different life before coming to the Hazbin Hotel universe and that could be delved into. For example, his family, his upbringing, and how those things might have shaped his current self.
Maybe they could go on a road trip together. Along the way, they discover new things about each other and their pasts. They might run into old friends or foes from their respective storylines, which could add drama and conflict to the fanfiction. For example, they could encounter someone who has a grudge against Adam and Chelsea has to decide whether to stand by him or not.
Well, a really interesting plot could be that Prince Adam's curse starts to affect Belle in some strange way, like she starts to have visions of his past. Then they have to figure out how to stop this new development. Also, they could go on a journey to find a long - lost relative of Adam's who might have a way to break the curse completely. And there could be a part where they face a magical being who tests their love for each other in unexpected ways.
One interesting plot idea could be that Lucifer, seeing Adam's pure and innocent nature, decides to test him in various ways. He might create illusions of worldly temptations to see if Adam can resist. Another could be that Adam, being curious about the fallen angel, tries to understand Lucifer's fall from grace and in the process, they form an unlikely friendship that challenges the norms of heaven and earth.
One idea could be to explore a future where Batman Beyond has to face an old enemy from the original Batman's time that has been resurrected with new, advanced technology. This would create a clash of old and new styles of combat and detective work.
One idea could be that Adam and Emma discover a hidden power within the drops of eternity that can change the fate of their world. They then have to protect this power from those who would misuse it.
One plot idea could be that Crowley and Aziraphale try to hide Adam's true nature from the other celestial and infernal beings. They might pretend he's just an ordinary human boy while secretly teaching him about his powers. For example, they could take him on trips to historical and magical places to help him understand the balance between good and evil.
A third idea is that there is a curse placed on the entire kingdom that makes everyone forget who they are, including Prince Adam and Princess Belle. They have to work together to figure out their identities and break the curse. Along the way, they might have some funny moments where they mistake each other for someone else, but gradually they start to rediscover their love for each other through small, kind gestures and shared memories.