Maybe it's a one - night - stand. Astrid wakes up one day realizing she's pregnant and has to track down the man she barely knows. This would lead to a whole lot of drama and self - discovery.
It could be her long - time boyfriend. They've been in a loving relationship for years, and this pregnancy is the next step in their journey together.
Perhaps it's a human boy who accidentally wandered into the fairy world. Tinkerbell, being curious, interacted with him, and in a magical turn of events, she became pregnant. This would create a lot of drama as the fairy world and the human world don't usually mix in such an intimate way, and there would be a struggle to figure out how to handle this situation.
It could be her long - time boyfriend. They might have been planning for a family in the future, but the pregnancy comes as a bit of a surprise earlier than expected.
Another possibility is that it's a result of some sort of experimental jutsu gone wrong. So there may not really be a traditional 'father' in the sense, but rather it's a consequence of Naruto's own actions in the world of ninja magic.
It could be her long - time boyfriend. They've been in a loving relationship, and this pregnancy is a natural step in their relationship journey.
It could be another hybrid like herself. Maybe there's a new character who is also part vampire and part human, and they fall in love and conceive a child.
It could be Flynn Rider. Since they have a strong relationship in the original story, it's very likely that he is the father. They are in love and have been through a lot together, so it would make sense for him to be the one.
It could be one of her close allies or friends. Maybe someone she has had a long - standing relationship with in the original story. For instance, if there is a character who has always been by her side and they share a deep emotional bond, he could be the father.
There's also the possibility that it was an accident involving a time - traveling character. Perhaps someone from the future came back in time and accidentally caused Frieza's pregnancy through some unforeseen interaction. This would open up a whole can of worms in terms of time - travel paradoxes and how it affects the future of the 'Dragon Ball' universe.
It could be Asuma. Since they had a relationship in the original series, it would be a logical choice. Their relationship was a significant part of the story, and having him as the father would add depth to the fanfiction, with the story exploring their future together as parents.
It could be Finn. They have a strong bond in the movies, and it would be an interesting dynamic to explore their relationship as they prepare for a child together.