Perhaps it's a new kind of monster that was created through a combination of human technology and some ancient, unknown force. This new monster mated with Godzilla in some unexpected encounter, and now she's pregnant. There could be a whole backstory about how this new monster came to be and how it interacted with Godzilla.
In the fanfiction, the father could be a shape - shifting alien that took on a form similar to Godzilla to deceive her. After the encounter, Godzilla became pregnant. This would add an element of mystery and deception to the story, as the true nature of the father is not immediately clear and could have all sorts of implications for Godzilla and the world around her.
Maybe it's a completely new character introduced in the fanfiction. This new character could have some special powers or a unique connection to Naruto that results in the pregnancy.
It could be Beast Boy. Their relationship in the original series has some chemistry, and in the fanfiction, it would be an interesting twist if he were the father. Maybe their relationship takes a new turn when Raven discovers she's pregnant.
It could be Rick. They have a strong bond and connection in the series, so it's a possibility that he could be the father in the fanfiction.
If we follow the more traditional route, Mako could be the father. They had a relationship in the show, and it would be a natural progression for them to start a family. Their relationship had its ups and downs, and the pregnancy could be a new chapter in their story together.
Well, perhaps in the fanfiction, Godzilla's pregnancy is part of a prophecy. The story could then revolve around the search for the meaning of this prophecy. Scientists or other characters might try to study Godzilla during her pregnancy to understand how it could impact the world. And there could be a race against time to either protect Godzilla and the unborn or to prevent a potential disaster that the pregnancy might bring.
Well, perhaps it could involve Godzilla's transformation in some way due to the pregnancy. He might become more protective and have to find new ways to co - exist with humans while ensuring Miki's safety during the pregnancy. It could also show how Miki adjusts to carrying a creature as powerful as Godzilla's offspring.
While Peeta is the obvious choice, some fanfictions might explore the idea of Gale being the father. This could add a whole new layer of drama and conflict. Maybe there was a moment of passion between Katniss and Gale before she fully committed to Peeta, and this led to her pregnancy. However, this would be a more controversial take as it goes against the main narrative of Katniss's relationship with Peeta in the original series.
It could also be a new character introduced in the fanfiction. Maybe a powerful demigod from another camp who Annabeth meets during a diplomatic mission. This would create a whole new set of drama and conflict, as Annabeth would have to deal with her feelings for Percy and this new person, as well as the implications of having a child with someone other than Percy.
It could be one of her close friends from the guild. Maybe Jellal, considering their complex relationship in the original story. There's already a lot of history between them, and this could be a new development in their relationship.
Maybe a new character that was introduced into the story specifically for this plotline. This new character could bring a lot of mystery and new storylines related to the pregnancy.