Once upon a time, there was a little girl named Lily. She lived in a small village surrounded by beautiful meadows. One day, she decided to explore the forest near her village. As she walked deeper into the forest, she discovered a magical stream. The water sparkled like diamonds and made a soothing sound. Lily sat by the stream and watched as little fairies emerged from behind the flowers. They danced around her, and one of them even gave her a flower that could grant wishes. Lily wished for her village to always be happy and prosperous. From that day on, the village thrived, and Lily was known as the girl who brought good fortune.
One common theme is mystery. Since it's related to 'phantom', there's often an air of mystery around the character of Paulina. Another theme could be love and relationships, exploring how Paulina interacts with other characters in a romantic or platonic way.
Alexis might confront Beckett directly. She could say something like 'I think you're cheating on me. What's going on?' This is a very straightforward approach.
I don't know who Alexis is in this story without reading it. But it's likely that Alexis is either the main character or an important figure in the events that unfold in the 'creepy subway' setting.
A plot could involve Paulina getting a special power that links her to the ghost world somehow. Danny Phantom discovers this and has to help her control it. During their time together, they grow closer. Paulina begins to question her feelings for Danny, both as a human and as Danny Phantom. And there could be a sub - plot where another ghost tries to use Paulina's new power for its own evil purposes.
One common theme is transformation. Paulina often has to transform her view of Danny from a loser to someone she can respect or even like. For example, in many fics, she starts to notice Danny's heroic side as Danny Phantom.
A lawyer could be an important character. This lawyer takes on Alexis's case, believing in their innocence. The lawyer has to battle a corrupt legal system or powerful opponents who want to see Alexis locked up for good. The fanfic could show the lawyer's strategies and how they build a case in Alexis's favor.
Perhaps there have been some rumors or whispers in their fictional world that have reached Alexis' ears. Even if they are baseless, they can plant the seed of doubt in Alexis' mind, making her think that Kate is cheating.
She could be defensive of Beckett. Since Alexis probably has a good relationship with Beckett, she may try to convince Castle that he's wrong and that Beckett didn't mean any harm. For example, she might tell Castle about all the positive things Beckett has done for her.
One common theme is the exploration of their relationship. Whether it's a friendship or a budding romance, it's often at the center of the story. For example, in many fanfictions, Danny tries to protect Paulina from ghosts, which shows his care for her.