Bulma should definitely be included. As Vegeta's wife and the mother of his baby boy, she can add a lot of emotional depth to the story. She can be the one who balances out Vegeta's strict training with love and care for their son.
Scott would be a great character to include. He's Stiles' best friend and could offer support and advice on raising the baby boy. Lydia would also be good. She's intelligent and could help with any strange or supernatural situations related to the baby. And Derek, with his brooding nature, could provide an interesting dynamic, perhaps as a sort of mentor figure to the baby as he grows up.
Definitely Superboy himself. He is the central character. Then, Superman could be a great addition. He could act as a mentor to Superboy in dealing with the baby situation. Lois Lane could also be included. She could be the one providing some practical advice on taking care of a baby. And of course, the baby character is essential.
One interesting fanfiction could be about Vegeta training his baby boy from a very young age. He passes on his Saiyan warrior skills and teaches him about honor and strength. For example, in this story, the baby boy might struggle at first but then gradually show great potential.
Piccolo would also fit well. He has a history of fighting alongside Goku and has a complex relationship with Vegeta. His calm and strategic thinking could add depth to the fanfiction, especially in battles where they need to outwit the opponent.
Goku could be a great addition. Maybe he could offer some advice to Vegeta about his tail based on his own Saiyan experiences. Another good character would be Trunks. He could be involved in a story where he discovers something new about his father's tail.
Danny himself is a must - include. His powers and his dual identity would add a lot of interesting elements. Tucker and Sam are also great choices as they could be Danny's support system while dealing with baby - related situations. Jazz could be included as she often has a more mature and understanding perspective. And of course, Danny's parents, who might be clueless about what's really going on with the baby but still add a lot of humor.
Raj could be a great addition. He might be the nervous uncle who is always a bit afraid of holding the baby but tries his best. His attempts at babysitting could lead to some really funny situations, like accidentally mixing up the baby's formula with his coffee.
Definitely Harry Potter. He was a good friend of Lupin and Tonks, so he could be like an uncle figure to the baby. He could visit often and share his own experiences growing up in the wizarding world, giving the baby some valuable advice.
Master Roshi could also be a great addition. His old - school ways and his comical reactions to Vegeta and Bulma's relationship can be really entertaining. For instance, he could give some really strange relationship advice to Vegeta based on his own limited understanding of modern relationships.
There is a fanfiction called 'Baby Vegeta's Training'. In this, it details how baby Vegeta, despite his small size, still tries to train and become stronger. It's interesting as it gives insights into his character and his unwavering determination to be the best, even as a baby.