Some fanfictions focus on how they handle their relationship once they're together. For instance, they might have to deal with jealousy issues. Castle could be jealous of Beckett's old friends or partners, and Beckett might be jealous of Castle's female fans. And then there are the plotlines where they plan their future together, like thinking about moving in or getting married, all while still solving crimes side by side.
Often, there are plotlines where they get together secretly at first. Maybe they don't want to deal with the complications at work, so they keep their relationship under wraps. But then, of course, there are always those moments where they almost get caught, which adds to the drama. There are also plotlines where an external factor, like a new detective joining the team, makes them realize their feelings for each other more strongly.
It could also be a fanfic that takes place in an alternate universe. In this universe, the events of 4x23 didn't happen as they did in the show. Maybe Beckett didn't become a detective in the same way, and Castle meets her in a completely different situation. They then start to solve mysteries together in this new setting.
One common theme is physical injury. For example, Beckett might get hurt during a case, and Castle has to deal with his worry and protect her. Another theme is emotional hurt, like when they have a misunderstanding or an argument that causes pain to their relationship.
One common theme could be the anticipation and excitement of new life. The story might focus on how Beckett and Castle prepare for the baby, like decorating the nursery or choosing names. Another theme could be the challenges they face during the pregnancy, such as health scares or adjusting to the idea of becoming parents. It could also explore how their relationship evolves during this time, growing deeper as they share this special experience.
One possible plotline could be that the baby has some sort of special ability or is in some way connected to a mystery they have to solve. Maybe the baby's birth coincides with a strange series of events in the city, and Castle and Beckett have to use their skills to protect the baby and figure out what's going on.
A prevalent theme is the balance between their professional and personal lives. They have to figure out how to be great detectives while also being present and loving parents. This creates a lot of interesting plotlines in the fanfiction. Sometimes they struggle with leaving the baby to go on a case, or they bring the baby - related chaos into their work environment in a humorous way.
One common element is the underlying tension. Before the kiss, there's usually a lot of unspoken feelings between Castle and Beckett. Another is the role of the cases they solve together. It often brings them closer and sets the stage for the kiss. Also, the use of dialogue is important. They might exchange some meaningful words right before the kiss that express their true feelings.
One common plotline is that after a period of separation, they accidentally meet again in a new situation. For example, they might both be involved in a mission to save the Fire Nation from a new threat. This shared purpose brings them closer and makes them realize their feelings for each other again.
Some fanfictions center around their cases. They might expand on a case from the show that seemed really interesting but was not fully developed. For instance, a story could be written from the perspective of Castle and Beckett when they were on a particularly dangerous undercover mission. These types of stories add more depth and detail to the events that happened in the show.
One popular 'castle beckett fanfiction' story could be about their adventures in an alternate universe where they solve crimes in a steampunk - style city. Another might focus on their relationship development during a long - undercover mission.
One of the plotlines could be when they face a big threat to their relationship. Maybe an old flame of Castle's shows up or there's some misunderstanding at work that makes Beckett question their relationship. But through communication and trust, they overcome these obstacles and their relationship becomes even stronger. This kind of plotline shows the resilience of their love for each other.