Freddy might be involved. He could be Bonnie's friend and offer support during the pregnancy. Also, Chica might be there to give Bonnie some advice on dealing with the situation, especially if there are any food - related aspects to consider in the story.
The Puppet could be a key character. It has always had an air of mystery in the FNAF universe, and it might play a role in Bonnie's pregnancy, perhaps as a protector or a guide. And then there's Foxy. Foxy could be another important character, either as a curious observer or someone who gets involved in unexpected ways, like helping Bonnie find a safe place for when the baby arrives.
Chica could also be a main character. She could be the one who tries to comfort Bonnie while he's sick. Maybe she brings him some virtual food or something to cheer him up. And Foxy might be another important character. He could be the one who goes on adventures to find a cure or a way to fix Bonnie. He's the more adventurous type, so it would make sense for him to be the one looking for solutions outside the normal areas in the pizzeria.
The Lone Wanderer is likely to be involved. They have a pre - existing relationship with Amata from the game. Her father, the Overseer, might also play a role, either in supporting or opposing the situation. Other characters from Megaton or Tenpenny Tower could potentially be involved as well.
Finn could be involved if the fanfiction wants to explore a relationship with him as the possible father. He was an important part of Rachel's life in the original series, and his reaction to the news would be significant.
Tatsumi is very likely to be involved as he has a significant relationship with Esdeath in the original story. Her subordinates in the Jaegers might also be part of the fanfic. They could be shown as being protective or having mixed feelings about her pregnancy.
Her partner would be a very likely character to be involved. They could be the source of support, or in some cases, the source of conflict if they have different views on the pregnancy. Her best friends are also likely to be in the fanfic. They might be there to throw baby showers, give advice, or just be a shoulder to cry on.
Obviously, her partner would be very involved. If we follow the relationships in the Winx Club, it could be Timmy. He would be there to support Tecna through the pregnancy, helping with things like getting the right magical supplies for the baby. Another character could be Bloom. As the leader of the Winx Club, she would offer her friendship and support, and might also be involved in protecting Tecna during this vulnerable time.
The father of the baby is of course a key character. He could be a mystery man at first, or someone from her past. If it's a star - crossed situation, maybe he's from a rival group or has some sort of conflict that makes their relationship complicated. There could also be doctors and nurses in the fanfiction who are taking care of Taylor during her pregnancy.
Finn is very likely to be involved. If he's the father, he would have a huge role in the story. He'd need to deal with his own feelings about becoming a father so young and how it affects his football and Glee club activities. Quinn could also be involved. She might offer Rachel advice based on her own experience with pregnancy, even though their situations were different. And of course, Mr. Schuester would be there. He'd be like a mentor to Rachel, guiding her through the tough times and making sure she still has a place in the Glee club.
Armin could be one of the main characters. He might be the one who offers the most logical advice to Eren during his pregnancy. For example, he could help Eren figure out how to deal with the medical aspects if the world in the fanfiction has different rules for male pregnancy. Another character could be Mikasa. She would probably be very protective of Eren, just like she always is. She might be the one to stand up for Eren against any discrimination or threats he faces because of his pregnancy.
Esposito and Ryan are very likely to be involved. They are Castle's friends and colleagues, and they would probably be there to support the couple. They might offer their own brand of humor and help out in practical ways, like throwing a baby shower for Beckett and Castle. Also, Martha, Castle's mother, would surely be a central figure. She could offer her wisdom on pregnancy and child - rearing, and add some comical moments with her unique personality.