Perhaps a storyline where Emerald's pregnancy is a result of some sort of experiment gone wrong. This could then lead to a race against time to find a cure or solution before the pregnancy takes a more dangerous turn, all while dealing with the internal and external conflicts in the RWBY universe.
One possible storyline could be that Cameron, being an advanced machine, discovers she has some sort of malfunction that mimics pregnancy symptoms. This could lead to her trying to understand human pregnancy in order to fix herself, while also causing confusion among the human characters she is with. They might initially think she has been reprogrammed by the enemy, but as she tries to figure it out, she begins to understand more about human emotions related to pregnancy like fear and anticipation.
In some RWBY Blake pregnant fanfiction, the story could focus on the cultural implications. Since Blake is a Faunus, there could be unique Faunus traditions related to pregnancy. Maybe her pregnancy is seen as a symbol of hope for the Faunus community. The story could also explore how the human characters in RWBY react to this Faunus - related aspect of the pregnancy, and whether it helps bridge the gap between the two races in the RWBY world.
One possible storyline could be that Zanessa discovers they are pregnant unexpectedly. They then have to deal with the reactions of their friends and family. Some might be overjoyed while others could be concerned about their future. They would need to make decisions about their careers and how to balance impending parenthood with their personal and professional lives.
One possible storyline could be about how the pregnancy affects Celestia's daily duties in her magical realm. She might have to delegate more tasks as she experiences the physical and emotional changes. Another could be the discovery of the pregnancy and how the other characters in the story react, whether it's with joy, concern, or a mix of both.
A storyline might involve Lagoona trying to balance her school life at Monster High with her pregnancy. She could be determined to keep up with her studies and participate in school activities, but find it increasingly difficult as the pregnancy progresses. There could also be a sub - plot about her relationship with her partner, and how they grow closer or face difficulties together during this time.
A possible story might be that Aisha is pregnant and she decides to take a break from the Winx Club activities for a while. During this time, she could start a diary or a record of her experiences for the baby to read in the future. Her friends from the Winx Club could visit her regularly and she could be teaching them about the new magical aspects related to her pregnancy. There could also be a sub - plot where she has to deal with the expectations of her family regarding the pregnancy.
A story could also focus on the magical or unique aspects of their pregnancy if there are any in the fictional world they belong to. For instance, if there are special powers or abilities that the babies might inherit, they could start to sense those during the pregnancy and it could lead to some interesting adventures as they try to understand what it all means.
One possible storyline could be that Castiel's pregnancy is a result of some magical or otherworldly occurrence. His friends in the story might be in a panic trying to figure out how to help him through the labor. Maybe they have to search for a special midwife or healer who can understand the unique nature of his situation.
A third storyline could be Erin's self - discovery during pregnancy. She might find new strengths within herself as she prepares to become a mother. She could also face insecurities from her own past, like if she had a difficult relationship with her own mother, and be determined to break that cycle for her child.
A storyline could revolve around the pregnancy being a surprise to both of them. They could initially be in denial or scared, but then gradually come to terms with it. Maybe they start making plans for the future, like finding a safe place to live and raising the child away from the chaos of their usual supernatural battles. They might also discover new powers or abilities related to the pregnancy, which could be both a blessing and a curse as they try to figure out how to control them.