Yamcha could potentially betray Bulma. Even though they have a history together, in a fanfic scenario, he could be jealous of Bulma's growing closeness with Vegeta or her scientific achievements. So, he might do something to undermine her, like spreading false rumors about her work.
Definitely include Whis. His knowledge and his ability to train Goku can be a great plot point. Beerus, the God of Destruction, can also be included. His temper and his power can create high - stakes situations in the fanfiction. Additionally, Chi - Chi could be added. Her possessive love for Goku can create conflict when it comes to Bulma's friendship with Goku. And Future Trunks is another character that can bring a sense of mystery and urgency to the story with his knowledge of future events.
It could be Frieza. He might see Bulma as a valuable asset due to her intelligence and knowledge of Earth's technology. He could kidnap her to use her to build powerful weapons or devices to help him regain his power and dominance in the universe.
Another character could be Dr. Briefs, Bulma's father. In the alternate universe, he might have a more prominent role in bringing Vegeta and Bulma together. For example, he could be the one who arranges for Vegeta to work on a project with Bulma, which starts their relationship on a more professional note that gradually turns into something more personal.
The main characters would obviously be Vegeta and Bulma. Vegeta is the Saiyan prince, a powerful and often brooding character. His presence brings a sense of strength and an otherworldly quality to the story. Bulma, on the other hand, is a human, a brilliant scientist. She's strong - willed and independent, which makes for an interesting dynamic when paired with Vegeta, especially during her pregnancy.
Obviously, Goku and Bulma are the main characters. Goku, the powerful Saiyan with his incredible strength and love for fighting. And Bulma, the smart scientist who is always inventing things.
Bulma and Goku are the main characters. Bulma is known for her intelligence and her somewhat feisty nature. She's not afraid to speak her mind, especially when she feels wronged. Goku, with his innocent and straightforward personality, sometimes doesn't fully understand the implications of his actions. In a 'bulma goku mistake fanfic', their contrasting traits are what drive the story. For instance, if Goku accidentally eats all of Bulma's special food meant for an experiment, her reaction based on her assertive nature and his reaction based on his cluelessness about the importance of the food can create a lot of drama and humor.
Frieza or his remnants could be antagonists. They might see the unborn child as a potential threat in the future, especially if it has strong Saiyan powers. So they could plan to attack Bulma to prevent the birth.