Well, obviously Emma and Hook are main characters as the parents of the baby. Emma, with her strong magic and determination, and Hook with his swashbuckling charm and loyalty. The baby, of course, is also a central figure in the fanfiction, even if it might start as a newborn and grow throughout the story.
One interesting storyline could be the baby having some sort of magical ability inherited from both Emma and Hook. Maybe the baby can control water like Hook and also has Emma's strong will, which helps them in various adventures in Storybrooke.
Yes, there might be some available on various fanfiction websites. You can try searching on platforms like Archive of Our Own (AO3) or FanFiction.net. Just be sure to check the tags and ratings to find the kind of story you're interested in.
I'm not sure of specific popular ones off - hand. But you can look at the most - read or highest - rated stories on fanfiction sites with the relevant tags.
One popular storyline could be about how they deal with the unexpected pregnancy in a world full of magic and danger. Maybe they have to protect the unborn child from villains who want to use its power. Another could be the emotional journey they go through, from shock to acceptance and finally to excitement for their new family.
In the fanfiction, perhaps Emma's pregnancy is a magical one. Maybe it was the result of some long - lost magic that got reawakened. Hook would be both excited and a bit scared. They could go on a journey to find a way to ensure the baby's safety in a world full of magic and curses. And Emma might struggle with her usual role as a savior while being pregnant, but Hook would be there to support her every step of the way.
In a fanfiction of Emma's time travel in OUAT, she might accidentally travel to a time when the Evil Queen was just starting to turn dark. Emma could try to befriend Regina and prevent her from becoming the Evil Queen. This would involve a lot of heart - to - heart talks and Emma showing Regina that there is another path. It could also lead to some really interesting interactions with other characters like Snow White and Prince Charming, who might be suspicious of Emma's presence in that time period.
Snow White and David are often main supporting characters. They are Emma's parents, so they would be there to support her during the pregnancy. They might offer advice on parenting and how to deal with the challenges that come with it.
One idea could be that they face challenges in their relationship while preparing for the baby. Maybe Hook is worried about being a good father because of his past. Another could be that Emma's magic has an unexpected reaction during her pregnancy, like protecting the baby in a magical way. And a third idea is that they discover a prophecy related to their unborn child which forces them to go on an adventure to protect their family.
A popular type of Emma time travel fanfiction in OUAT could be her traveling to different realms during different time periods. For example, she might end up in Wonderland in the past and have to deal with the Red Queen. This would put her in a whole new set of challenges as she tries to find her way back home. She might also meet some versions of the characters she knows in different forms, which would make for an interesting story as she tries to figure out who is friend or foe.