In the fanfiction, perhaps Sam betrays Danny in a more complex way. She could be tricked by a powerful ghost into believing that Danny is a danger to the town. So, she might take actions against Danny that she later regrets. This would add a lot of drama and conflict to the story.
One possible scenario could be that Sam betrays Danny's secret identity to someone he doesn't trust, like a ghost hunter. Maybe she does it out of jealousy if Danny starts getting closer to another character.
Perhaps in the fanfiction, Danny is betrayed by a new ally he trusted. This new character could have joined Danny in his fight against evil ghosts, but in reality, they were working for a more powerful and evil ghost all along. They might use Danny's trust to learn about his weaknesses and then expose him to danger, leaving Danny feeling hurt and alone, having to reevaluate who he can trust in the future.
In some fanfictions, it could happen during a moment of vulnerability. For example, if Sam gets hurt while they're on an adventure, and Danny is really worried about her. As she recovers, Danny realizes how much she means to him and they share a kiss. Or maybe they get stuck in a ghost - created alternate dimension where they think they might not get out. In that desperate situation, they confess their feelings and kiss for the first time.
One interesting scenario could be when they share their first kiss during a dangerous ghost - fighting situation. Maybe they think they won't make it out alive and finally confess their feelings through that kiss.
Well, it could be that there is no traditional antagonist. Sam's betrayal could be the main source of conflict, and she could be seen as the antagonist in Danny's eyes for that time being. But if there has to be another force, it could be the entity that influenced Sam to betray Danny in the first place. For example, a powerful and manipulative ghost that has its own agenda and uses Sam as a pawn.
One possible storyline could be that Sam is influenced by a new, mysterious character in town. This character might be using some sort of mind - control or persuasion power on Sam, making her act out of character and cheat on Danny. Another idea is that Sam and Danny have a big fight over Danny's ghost - hunting duties. Sam feels neglected and in a moment of weakness, she might get involved with someone else.
Some fanfictions might have the first kiss during a school event. For example, at a dance. Danny and Sam might be dancing, and as they look into each other's eyes, they finally give in to their feelings and kiss. This setting adds a bit of normalcy to their otherwise extraordinary lives.
One possible scenario could be Danny getting injured during a fight with a powerful ghost. Maybe he underestimated the ghost's new power and got hit by a strong energy blast that left him with a serious injury.
One possible scenario could be Danny getting bullied at school. Maybe some of the other students find out about his ghost powers and they target him out of fear or jealousy. Another could be that he gets injured during a ghost attack that takes place on school grounds while he's trying to protect his classmates.
One interesting story could be about Danny and Sam going on a ghost - hunting adventure together. They might discover a new type of ghost that has unique powers and they have to figure out how to defeat it using their combined skills.
Love and friendship are common themes. Their relationship, whether it's a budding romance or a deep platonic bond, is often explored.