Don't forget about potential love interests. If she has a boyfriend in the story, he would be a major part of the pregnancy journey. He could be excited, scared, or even hesitant about the whole situation. And there could also be other characters from the show who pop in and out, adding their own flavor to the story, like neighbors or extended family members who have their own opinions and advice about the pregnancy.
Well, aside from the main Avengers, there could also be other supporting characters. For instance, Jarvis, Tony Stark's AI, might play a role as Pepper Potts could interact with it while dealing with Stark - related matters. Also, Happy Hogan, Stark's bodyguard and friend, could be involved in some way, perhaps providing security during Pepper's interactions with the Avengers.
There could also be appearances from other characters like Smackle. Maybe she's initially uncomfortable with the idea of wearing a bikini but through her friends' support, she gains confidence and has a great time at a pool party or beach outing in the fanfiction.
Definitely Torbjorn. Since he has a connection with Bastion in the original Overwatch lore, he would be a central character. Reinhardt could also be involved. His chivalrous nature might lead him to protect Bastion if he saw it was in trouble. And of course, Mercy. She's always there to heal and help, so if Bastion gets damaged during the story, she would be there to patch it up.
Riley Matthews is often involved. She has a bubbly personality, so it's easy to imagine her being part of tickle - related scenarios, either as the one being tickled or tickling others in a friendly way.
Also, any friends that Renesmee has made throughout her life could be involved. They might be there to offer moral support, or there could be some who are jealous or envious of her situation, which could add some drama to the fanfic.
Magnus Bane could be involved. He has knowledge of both the magical and vampire worlds, so he could offer advice or help. Clary Fray might also be there, as Isabelle's friend, she would be supportive during the pregnancy. And of course, Simon, who has his own connections to the vampire world through Raphael.
In the 'yugi turns into a girl fanfiction', apart from Yugi's main group of friends, there could be some new characters introduced. Maybe a mysterious figure who knows the secret behind the transformation and can either help or hinder Yugi. Also, Yugi's grandfather might play an important role. He could be worried about his grandson/granddaughter and try to find a solution to reverse the transformation. And of course, the spirit of the Millennium Puzzle, Yami Yugi, would also be involved, perhaps having a different kind of connection with Yugi in this new form.
Well, in a 'Girl Meets World' fanfic, the main characters would typically include Cory and Topanga's daughter, Riley. Her best friend Maya would also be a central figure. And of course, there's Farkle, who is an important part of their group. There might also be other characters from the original 'Boy Meets World' series making appearances in the fanfic, like Shawn Hunter.
Obviously, Miley Stewart and her father would be the main characters. Since it's about Miley being sick and her being Daddy's girl.
One possible interesting plot could be how the main character deals with the unexpected pregnancy while still trying to pursue her dreams. Maybe she has to balance school and the new responsibilities that come with pregnancy.