A great plot for a 'baby daddy fanfic' could be that the baby daddy is a struggling artist. He and the mother had a passionate relationship in art school. Years later, he's still trying to make it big when he discovers he has a child. He then has to balance his pursuit of art with his responsibilities as a father. He might use his newfound fatherhood as inspiration for his art, and along the way, he and the mother re - explore their relationship while dealing with the joys and challenges of raising a child.