A really interesting plot twist could be that the school has a secret passage or a hidden room that is somehow related to the demigod world. Percy and Annabeth accidentally discover it while exploring the school. Inside, they find ancient artifacts or prophecies that lead them on a new and dangerous adventure, which might involve traveling to a different dimension or time period.
Well, Percy might face some academic challenges at Annabeth's school. Since he's used to his own demigod training, normal school subjects could be a bit tough for him at first. For example, he could struggle with math or history classes.
It could be about Percy playfully teasing Annabeth in a light - hearted way. Maybe he teases her about her love for architecture, and she retaliates with her own witty remarks about his skills in the water. Their banter could be a way to show their close relationship and mutual understanding.
Maybe Percy would struggle to fit in at first. He's used to his own world and suddenly being in a regular high school could be quite a shock.
In the fanfic, when Percy goes to Annabeth's school, he could end up in trouble with the school authorities. Since he's not used to a normal school environment, his demigod abilities might cause some chaos. For example, if there's a pool at the school, he might accidentally show off his water - controlling powers. And he'll probably have to deal with normal school stuff like classes and bullies, which will be really interesting to see how he copes with it all.
Percy could meet the school bullies. And they might pick on him at first, but then be in for a big surprise when he shows his strength. Also, he might encounter some teachers who suspect there's something different about him. Maybe a science teacher who notices his quick reflexes during an experiment or a history teacher who is amazed by his knowledge of ancient mythology.
A plot twist could be that when Percy gets to the school, he realizes that Annabeth has disappeared. He starts to search for her and discovers that she has been lured into a trap set by an old enemy. This enemy has plans to use Annabeth as bait to draw Percy in and then defeat them both. Another interesting twist could be that as Percy is waiting for Annabeth, he is suddenly attacked by a group of disguised monsters. He has to fight them off while also trying to find Annabeth. And there could also be a twist where Annabeth has changed in some unexpected way, like she has lost her memory, and Percy has to figure out how to deal with this new situation while getting her home.
A plot twist might be that the goblins turn against Harry midway through his visit. They could be influenced by a dark wizard who has a grudge against Harry. This would completely change the course of his visit and force him to find a new way to achieve his goals in Gringotts. Another possibility is that the vault contains a magical item that has a mind of its own and tries to possess Harry when he touches it.
Maybe she's jealous of Percy's popularity at school. It could be that he always gets more attention, whether it's from teachers or other students.
One possibility is that Percy clashes with the school's jocks or popular kids. Since he's an outsider, they might pick on him at first. But then Percy shows them what he's made of, not with brute strength necessarily but with his quick thinking and his ability to outwit them. He could also get involved in a school competition, using his unique skills to help his team win.
There could be a school janitor who is actually an old demigod who retired from the hero business. He could give Percy some valuable advice based on his own experiences. And of course, Percy will surely meet Annabeth's classmates, some of whom could be friendly and some not so much, depending on how they react to the new boy in school.