One possible plot could be that the pregnancy is a result of some sort of magical or otherworldly event. Castiel might feel a strong sense of responsibility to protect Meg and the unborn child. He could use his angelic powers to keep them safe from various threats in the Supernatural universe, like demons or other malevolent forces.
I really like 'A Meeting of Opposites'. In this fanfiction, the author explores the idea of Castiel and Meg having to work together on a mission. It's a great read because it plays with their personalities. Castiel's naivete and Meg's cunning are both highlighted and as they interact, it creates a lot of tension and some really cool plot twists.
Character development is crucial. In fanfiction, we get to see different sides of Meg and Castiel. Maybe we see a more vulnerable side of Castiel or a less evil - more complex side of Meg. And the plot usually revolves around some sort of conflict, either between them or against a common foe.
The fanfiction might show Meg dealing with the physical and emotional changes of pregnancy while still being her tough self. She might have to fight off those who would try to harm her because of the baby. Castiel, on the other hand, would be by her side, using his powers when necessary. It could be a story of their growth as individuals and as a couple.
Another popular theme is the power struggle between them. Meg is a powerful demon and Castiel is an angel with his own set of powers. Fanfictions sometimes focus on how they use their powers against each other, or in some cases, how they learn to combine their powers for a common goal, which makes for some really exciting action - packed stories.
I really liked 'In the Shadows with Meg and Castiel'. It's a more introspective piece that explores their individual struggles and how they come to rely on each other. The descriptions in the fanfiction are really vivid, making you feel like you're right there in the Supernatural universe with them.
Well, to determine if Meg is a true story, you'd need to look at its source and the author's claims. Sometimes stories are inspired by real-life but have fictional elements added. So, it's not straightforward to give a definite yes or no.
It can show her vulnerability. When Meg is pregnant, she may be more exposed to the judgments of others, which can make her more self - conscious. This could be a chance to explore how she copes with that.