A possible plotline could be a moment of surprise or shock. For example, Annabeth might straddle Percy in a moment of panic during a training exercise gone wrong, like when a magical creature suddenly appears and she jumps on him for protection. Then they have a humorous exchange about the situation.
It could be a situation where they are in a tight spot in a quest. They need to quickly cross a dangerous area and Annabeth straddles Percy as he uses his powers to get them across, like if he has to swim through a treacherous underwater passage or fly over a chasm. During this, they share some heartfelt conversations about their trust in each other and their hopes for the success of the quest.
Maybe it's part of a prank. Annabeth decides to play a prank on Percy by straddling him while he's napping, and then he wakes up startled. This leads to a series of banter and light - hearted arguments between them as he tries to get back at her in some funny way. And throughout the story, their friendship and the dynamics of their relationship are explored in a comical and innocent way.
Another plotline could be that they are babysitting a group of demigod toddlers at Camp Half - Blood. The toddlers keep getting into mischief, like stealing nectar and ambrosia. Percy and Annabeth have to keep them in line, teach them about the rules, and also make sure they don't accidentally harm themselves with their budding powers. It could be a really cute and chaotic story.
Well, perhaps in the fanfiction, Annabeth betrays Percy's trust in a relationship way. She could start seeing someone else and use Percy's secrets against him to make herself look better in front of the new person. Or she might side with a group that Percy is against, believing their lies and false promises over Percy's warnings. This could lead to Percy feeling completely alone and having to find new allies.
Perhaps Annabeth is wrongly accused of a crime and is made a slave as punishment. Her friends, including Percy, try to prove her innocence while also dealing with the internal politics of the demigod society that allows such a cruel situation to exist. This could involve a lot of character development for all involved as they question the fairness of their world's laws and norms.
In this fanfiction, a plotline could involve Percy having to introduce Annabeth to his side of the family. This would be really interesting as it would show a whole new aspect of Percy's world to Annabeth. Another plotline could be Annabeth getting into trouble at school or with other demigods, and Percy having to step in as her father to resolve the situation. This would show how he uses his influence and authority in this new role. There could also be a plotline where Percy and Annabeth find out that there's a prophecy related to their new relationship. They would then have to figure out what it means and how to fulfill or avoid it, which would add a lot of tension and mystery to the story.
A possible plotline could be a mortal who becomes friends with Percy and Annabeth without knowing their true nature at first. As the story progresses, they start to notice strange things about their friends. Another plotline could involve a mortal who is caught in the middle of a demigod battle. They have to rely on Percy and Annabeth to keep them safe while also trying to understand what's going on.
In some fanfictions, this scenario could be used as a turning point in their relationship. Percy seeing Annabeth in such a vulnerable state could make him realize his deeper feelings for her. He starts to see her not just as a friend and teammate, but as someone he has strong romantic feelings for. This could lead to a series of events where he tries to court her in his own clumsy way.
One possible plotline could be that Percy is under some sort of mind control. Maybe a new villain has the power to manipulate his thoughts and actions, making him turn against Annabeth. For example, the villain could use Percy's insecurities about his past mistakes to drive a wedge between them. He might start by leaking some of Annabeth's secret plans to the enemy, causing her to be in danger without realizing Percy is the source.
Another plotline could be centered around Annabeth's jealousy when other characters show interest in Percy. So she's constantly thinking about Percy and how much she wants him all to herself. Her 'drooling' over him is a sign of her deep - seated feelings that she might not fully express outwardly all the time.
One plotline could be that they face danger from an old enemy who sees the unborn child as a threat. So they have to protect themselves and the baby. Another could be that Annabeth has some premonitions about the baby's future and they embark on a quest to understand what it means.
One possible plotline could be Percy going on a desperate search for Annabeth. He might start by retracing her last known steps, asking all their mutual friends and allies if they've seen her. Another could be Percy having to face some old enemies alone in his search, as Annabeth was usually the one who strategized with him. And he could also discover some hidden secrets about Annabeth's past during the search that he never knew before.