His relationship with Chi - Chi would be very different. Instead of being her husband, he's now like a son to her. She would be super protective. And with Gohan, it would be more like they are brothers. Gohan would have to look out for his 'baby father'.
With Vegeta, it would be quite interesting. Vegeta might initially see baby Goku as a weakness, but then he could start to respect the power that even a baby Goku has. And his friends like Krillin would be more like caretakers. They would be constantly worried about Goku's safety and development in his baby form.
For Bulma, she would probably be more of a mother figure to baby Goku. She'd be using her intelligence to figure out how to take care of him and get him back to normal. His relationship with Master Roshi would also change. Roshi might see it as a chance to train Goku in a different way, starting from a very basic level since he's a baby now.
The team as a whole would become closer as they united to take care of Keith. His transformation into a baby would bring out different sides of each character. They'd have to rely on each other more, communicate better, and work together in new ways. For example, they'd need to share babysitting duties, which would lead to more interactions and a deeper understanding of each other.
Well, with Sasuke, their relationship would become more of a protective - protectee one. Sasuke, who usually has a rivalry with Naruto, would now feel responsible for protecting this baby Naruto. With Sakura, she would be more motherly towards him. She might be the one constantly fussing over him, making sure he's clean and fed.
His relationship with Naruto might change. Naruto could be more protective of Kakashi as a girl. He might see her in a different light, like an older sister figure. With Sasuke, there could be some initial awkwardness. Sasuke, who is used to Kakashi as a male, might not know how to interact with him as a girl at first. And with Sakura, they could form a closer bond as girls, sharing things that only females in the ninja world might understand.
Well, with Kakashi, he might be more cautious in how he trains Sasuke. As a girl, Kakashi might have to consider different aspects of training, like physical limitations that might come with the female form. His relationship with his clan members, if they were still around, could also be different. They might have different expectations of a female Sasuke. And when it comes to the other male ninja in the village, some might be attracted to him, which would create some awkward or interesting situations.
His relationship with his enemies would change significantly. Voldemort or his Death Eaters might not recognize Harry as a rabbit at first, which could give Harry an advantage in some ways. However, if they did find out, they might see it as an opportunity to either capture or harm him more easily. Among his friends in Gryffindor, they would all be very concerned. Neville, for example, might try to use his knowledge of Herbology to find a way to reverse the transformation. And Ginny would be especially protective, seeing Harry in such a vulnerable state as a rabbit.
His relationship with MJ would become very different. Instead of a romantic partner, she might become more of a protective caretaker. She would have to deal with a baby - like Peter, which could be both challenging and endearing.
His relationship with Sasuke could become more complex. Sasuke might be both envious of Naruto's new power and also worried about Naruto losing his humanity in the dragon form. Sakura could be initially scared but then determined to help Naruto control his form, which would strengthen their friendship. His relationship with Kakashi would change as Kakashi would now have to mentor Naruto in a different way, guiding him to use his dragon powers for good and not let them consume him.
Among the Nordic countries, if Canada turns into a girl, they might treat her with more chivalry. Finland could be really friendly and share some of his own experiences with dealing with a different kind of identity. Sweden might be a bit quieter but still show his support in his own way. Norway could be a bit more standoffish at first but then come to accept her new self as part of the group.
With Kairi, they could become closer as girlfriends in a sense. They might share more girl - talk, like about their feelings for the boys in their lives. Kairi could also help Sora get used to her new female body, teaching her things like how to style her hair or choose the right clothes. But at the same time, there could be a bit of jealousy if other boys start showing interest in Sora.
His relationship with Toothless would change drastically. Instead of being the rider, he becomes like a little sibling or a young apprentice to Toothless. Toothless would have to be more protective and patient with Hiccup.