One idea could be a story about Bulma's inventions and how Baby Trunks gets involved in her experiments. For example, he could accidentally activate a device that sends them on an adventure through time or to a different dimension.
One idea could be a story where Bulma invents a new device to help Baby Trunks train more effectively. For example, she creates a gravity simulator that allows him to train in conditions similar to different planets.
Baby Trunks might learn to walk in the fanfic by imitating others or having a sudden burst of determination. It could also be that he gets inspired by seeing his older siblings walk freely and decides to give it a go himself.
One interesting 'Dragon Ball Baby Trunks' fanfiction could be about his training adventures with Goku. Maybe he discovers a new power during a sparring session. Another could be a story where Baby Trunks time - travels to a different era in the Dragon Ball universe and has to adapt to the strange new rules and enemies there.
A great plot twist could be that Baby Trunks is actually from an alternate future where things are very different. This would change the whole dynamic of how Bulma relates to him. Maybe in this future, Bulma didn't survive, and now he has come back to change the past.
One potential theme could be family. Vegeta's relationship with his son is explored, showing how a Saiyan warrior like him can adapt to fatherhood. Another theme might be growth, as Baby Trunks learns from Vegeta and Vegeta also grows as a person through this new connection.
Well, it could be that Vegeta, upon meeting Baby Trunks, realizes the importance of family in a new way. He might start to see the future differently, knowing that he has a son to protect and guide. There could also be some cute moments where Baby Trunks tries to imitate Vegeta's tough guy expressions, which would be quite endearing.
In a fanfiction, there could be a story where an enemy specifically targets Baby Trunks because of his Saiyan heritage. Bulma steps up as his protector, using her inventions to fend off the attacks. Along the way, they develop a stronger bond as they face this common threat together. Bulma also discovers new aspects of her own strength and courage in protecting Baby Trunks.
A really cool fanfiction could be set in an alternate universe where Vegeta and Baby Trunks switch bodies for a day. This would lead to all sorts of hilarious and heart - warming situations as they try to understand each other's lives better. Vegeta would see how difficult it is for Trunks to be in his shadow, and Trunks would understand his father's strictness a bit more.
One interesting fanfiction could be about Vegeta training Baby Trunks in a new and unique way. Maybe he takes him to a far - off planet with strange gravitational forces to toughen him up.