Well, Meredith could be a main supporting character. She might offer her own experiences and advice as a friend. Cristina could also be there, providing her unique, no - nonsense perspective on the whole pregnancy thing. Bailey might be another one, being the strict but caring doctor who ensures Izzie has a healthy pregnancy.
George could be a supporting character. He could be the friend who is always there to help out, like running errands for them or just being someone to talk to. Addison could also play a role, perhaps as a specialist who gets involved in some aspect of the pregnancy, offering her expertise.
One possible plotline could be their journey of preparing for the baby. They might struggle with finding the perfect nursery, dealing with financial aspects like buying baby stuff. Another could be how their relationship changes during the pregnancy. For example, they become more protective of each other.
Well, Alex and Olivia are the central figures. They might have different personalities. For instance, Alex could be more of an adventurous type, and now has to tone it down a bit to take care of Olivia and the baby on the way. Olivia could be a career - driven woman who now has to reevaluate her priorities with the pregnancy.
The main characters are clearly Alex and Justin Russo. Alex is known for her impulsive and fun - loving nature in the original show, and Justin is the more studious and rule - following sibling. In this fanfiction, their personalities would likely be put to the test with the unexpected situation of a pregnancy.
Dustin could be a main supporting character. He might be the one who offers comical but also some practical advice to Mike and Eleven. For example, he could try to help them figure out how to get baby supplies in a world where they're constantly dealing with the upside - down threats.
One of the main supporting characters could be Bella. As Renesmee's mother, she would likely be very involved in the pregnancy, offering advice and support. Another could be Edward. He might have some concerns about the situation but also be there to help protect the family. Alice could also be a key supporting character, perhaps using her gift to foresee any potential problems during the pregnancy.
It could be Blair. Blair might be a bit jealous at first but then come around to support Serena. Chuck could also be a supporting character, perhaps providing some advice to Nate from his own experiences in relationships.
Stiles could be a major supporting character. He would be there for Scott, giving him advice on how to be a good father. He might also crack some jokes to lighten the mood during tense times. Another could be Malia. She could help Lydia with her pregnancy cravings or just be a good friend to talk to.
The Lightwood parents could also be part of the story. They might initially be hesitant or have concerns about Jace and Clary having a baby so young in the Shadowhunter world, but later come around and offer their support, perhaps in terms of providing a safe haven or sharing their wisdom about raising a Shadowhunter child.
For Mason, you can give him some flaws. Maybe he's a bit of a procrastinator at first, not really taking the pregnancy seriously. But as he sees Alex's determination, he changes. Alex could be developed as a very independent character. However, the pregnancy makes her realize she needs to rely on others sometimes. You can show this through her interactions with her friends and family.
Since I don't know the exact details of this visual novel, I assume Izzie is one of the main characters. And there might be some dragon characters as well, perhaps a wise old dragon that guides Izzie or a young dragon that becomes her friend.