Pacifica might become more empathetic. Before having a baby, she was a bit spoiled. But now, she has to think about someone other than herself. Dipper, on the other hand, could become more responsible and protective. He was always the curious one, but now he has a family to look after.
For Pacifica, having a baby could make her more independent. She might break away from some of the old family traditions that she didn't like. Dipper would likely develop his leadership skills further. He has to make decisions for the well - being of his family now. He'll also become more patient as he deals with the baby's tantrums and needs.
Pacifica could develop a stronger sense of family values. Growing up in a wealthy but somewhat cold family environment, she now has the chance to create a warm and loving family of her own. Dipper will probably become more resourceful. He'll need to find ways to provide for the baby, whether it's getting a job or finding creative solutions to problems that come up in their family life.
In the fanfiction, the baby could have some special abilities or be a part of some sort of mystery. Since Dipper has had experiences with the supernatural in Gravity Falls, it's possible that the baby inherits something unique. This could lead Dipper and Pacifica on a new adventure to protect their baby from those who might want to use the baby's special powers for their own gain.
You could start by establishing the relationships between the characters before the pregnancy revelation. If Dipper and Pacifica are in a relationship, show how they interact with Wendy as a friend. When Wendy's pregnancy is announced, have Dipper react with shock and confusion. He might feel a sense of responsibility towards Wendy even if they're just friends. Pacifica could initially be jealous but then grow to be more empathetic as she realizes the seriousness of the situation.
Damon would likely become more protective and responsible. He might start to see the value in a more stable life. Elena would grow in her maternal instincts and become even more of a force to be reckoned with when it comes to protecting her family.
Travis might become more responsible. He could go from being carefree to being very protective of his family. Katie, on the other hand, might become more patient as she takes care of the baby.
Castle might become more responsible. He was always a bit of a carefree writer, but with a baby, he has to grow up a bit. Beckett, on the other hand, could become more empathetic. She was tough as a detective, but motherhood softens her edges.
Lexa would likely become more protective and perhaps a bit softer in her approach. She has always been a strong leader, but now she has a family to think about. Clarke, on the other hand, would probably use her medical knowledge more to take care of the baby. Her nurturing side would be more prominent.
Ichigo might develop more patience and a softer side as he becomes a father. He was always brave in battle, but now he has to be gentle with a tiny baby. Yoruichi, on the other hand, could become more nurturing. She was always independent and strong, but with a baby, she shows her maternal instincts.
Cat could start to show a more responsible side. She might learn how to cook healthy meals for the baby and manage the household better. Robbie could grow in his patience. Dealing with a baby can be frustrating at times, but he would learn to stay calm and handle the situation.
For Jane, she could develop a greater sense of patience. Babies can be unpredictable, and she'd have to learn to handle that. Maura might become more empathetic towards other parents, understanding the joys and struggles better. They both would likely become more family - oriented, with their decisions now revolving around what's best for the baby as well as themselves.
The two main characters are Dipper and Pacifica. Dipper is often depicted as the one with a thirst for knowledge about the strange and unusual in Gravity Falls. Pacifica, on the other hand, brings her own charm and background of a rich family. Their different personalities and backgrounds make for an interesting dynamic in the fanfiction when they are married.