One common plotline is the mystery behind the pregnancy. Is it a result of a forbidden love with another demon or some powerful entity? Writers often use this to create suspense.
Often, the pregnancy is depicted in a way that ties into the overall themes of the Supernatural world. It could be part of a prophecy or some sort of dark magic. Maybe she was cursed with the pregnancy, and it's now a race against time to either get rid of it or use it to her advantage. Fanfic writers might show her dealing with the physical and emotional toll of pregnancy while still trying to maintain her status among demons.
One common theme is power struggle. Abaddon is a powerful demon, so many fanfictions explore her battles for power, either against other demons or the Winchesters. Another theme is her backstory. Writers often delve into her past to give more depth to her character.
One common theme is the struggle between good and evil. Since Abaddon is a demon, her daughter often has to deal with the pull of her demonic heritage while also having the potential for good. For example, in many fanfics, the daughter may be tempted to follow in her mother's footsteps but then has to fight against that urge.
Often, there are plotlines where she teams up with Sam and Dean. They might not trust her at first because she's Bobby's daughter and they're worried about her getting hurt. But then she proves herself to be a capable hunter. There are also stories where she gets trapped in a different dimension or time period related to the supernatural and has to find her way back while dealing with the local supernatural threats there.
There are often plotlines where the reader is transported into the Supernatural universe and immediately runs into demon dean. Their relationship starts off rocky, with dean seeing the reader as an easy target or a nuisance. But as the story unfolds, they discover that they are linked in some way, perhaps by a prophecy or a shared past life. This leads to a journey of self - discovery for both of them as they figure out their relationship and their roles in the supernatural world.
In Supernatural fanfiction, a frequent plotline involving Sam and Bela Talbot is that of a reluctant partnership. Bela might drag Sam into one of her heists that ends up being more than she bargained for, and they have to face some terrifying supernatural entity together. Or perhaps Bela double - crosses Sam at first, but then realizes she needs his help to survive a situation. There are also plotlines where Sam tries to reform Bela, seeing some good in her that she doesn't even see in herself.
One common plotline is a female character getting pregnant unexpectedly, and the Winchester brothers having to protect her from supernatural threats because of the unborn child's special significance. For example, the child might be prophesied to have great power, attracting all kinds of evil forces.
A common plotline is the anticipation and excitement. Everyone around Hinata is excited for the new baby, like her friends and family. They might start preparing baby showers and gifts.
One common plotline could be Yugi dealing with the unexpected pregnancy and the reactions of his friends and family. Another might be the challenges he faces during the pregnancy, like health concerns.
A common plotline in Stalia pregnant fanfiction might be the way their relationship evolves during the pregnancy. They could grow closer as they anticipate the birth of their child. Or there could be some external threats or complications that put their relationship and the pregnancy at risk, like a supernatural threat in the Teen Wolf universe that they have to deal with while also preparing for the baby.