Often, it could begin with a sense of dread and confusion. Castle might receive a call or a message that something has happened to Beckett. And then he is immediately thrust into this situation where he has to identify the body. There could be a lot of chaos at the start, with police and other officials around the scene, and Castle trying to make sense of what's going on.
Typically, the fanfic starts with a build - up of tension. Maybe Castle and Beckett were working on a case together, and then suddenly Beckett goes missing. Castle starts to search for her frantically. Eventually, he gets a lead that leads him to a place where he is told there is a body that might be Beckett's. He approaches the situation with a heavy heart, filled with fear and anxiety about what he might find.
It might start with Castle getting the news of Beckett being in a dangerous situation, like a crime scene or an accident. Then he rushes to the location where her body is supposed to be.
One challenge could be the state of the body. If it has been damaged or decomposed, it would be difficult to identify. Another might be the lack of proper identification tools or information at the scene. Maybe there are no fingerprints available or dental records are missing.
Castle could initially deny it's her. He'd look for any sign that it's not Beckett, checking for details that are off. As he realizes it is her, he'd break down, crying uncontrollably. His world would shatter because she was such an important part of his life, and he'd be filled with regret for any unsaid words or things they didn't do together.
Castle might become obsessed with finding the truth about what happened. His writer's mind would start formulating theories and he would stop at nothing to get justice for Beckett, which could put him in dangerous situations.
He could become more withdrawn. Losing Beckett like that would make him hesitant to let people in again. He'd be more guarded, fearing another loss.
He would likely feel extreme shock. Just the sight of her body could send his mind into a tailspin. He might also be in denial at first, not wanting to believe that it's really her.
First, think about the characters. Decide who will be part of this arranged situation in the castle. Are they nobles, knights, or commoners? Then, consider the reason for the arrangement. Is it for political gain, to end a feud, or something else? Next, describe the castle. Its layout, its secrets, and its atmosphere will add depth to your story. Start with an interesting scene, like the moment the characters first meet in the castle, and build the story from there.
To start a 'castle baby fanfic', you need to establish the basic elements. Begin with the castle itself. Consider its architecture, the people living in it, and the overall atmosphere. For the baby, determine its origin. Is it a normal baby or is there something mysterious about its birth? You could start with a simple scene like the baby's first cry echoing through the stone hallways of the castle. This immediately sets the scene and draws the reader in. You can also introduce some conflict early on, like someone in the castle not wanting the baby there for some reason.
First, you need to decide on the setting of your castle. Is it a medieval European castle, or something more fantastical? Then, create your characters. They could be knights, nobles, servants, or even magical creatures. After that, think about the plot. It could be a love story, a quest, or a mystery.
Definitely Ben Tennyson. He's the center of the Ben 10 universe, so it's no surprise he's often in body switch fanfics. When his body is switched, it's not just about the physical change but also about how he'll use his alien forms in a different body. Gwen is also commonly involved. She has her own set of skills and a distinct personality, which can be a great contrast when she's in someone else's body. Then there are the various alien characters from the Omnitrix. If they end up in Ben's body or vice versa, it can create all sorts of chaos and interesting plotlines.
He could start by checking out some of the major fanfic websites like Archive of Our Own (AO3). It has a vast collection of fanfictions for various shows, including ones related to Castle and Beckett. Just use the search bar and type in relevant keywords like 'Castle and Beckett' and he'll likely find a lot of stories.