Chichi would be very shy and excited. She has loved Goku for a long time, so getting that first kiss would be like a dream come true. She might blush and stammer a bit, not knowing what to say. Goku, on the other hand, would be a bit confused at first. But then he would feel a warm feeling inside and realize that he really cares for Chichi in a special way.
Superman would likely be impressed yet also a bit competitive. He'd see Goku's strength and might feel the urge to prove himself. Batman would be calculating, taking mental notes on Goku's fighting style. Wonder Woman would admire Goku's tenacity and the way he uses his ki. The Flash would be astounded by Goku's speed, which might even make him a bit envious.
Superman would likely be impressed. He's used to being one of the strongest, but Goku's power levels would make him take notice. Batman would be his usual calculating self, studying Goku's moves for any potential threats or useful techniques. Flash would be excited to see someone who could keep up with his speed in a different way. Aquaman might be a bit more reserved, but still interested in this new kind of fighter from another universe.
His father might be extremely proud. After all, Goku has achieved so much, like protecting the Earth multiple times. He would look at Goku with admiration for his strength and kindness.
Vegeta would probably be both jealous and intrigued. Jealous because Goku has achieved a new level of power through this fusion, and intrigued because he wants to see how this new being fares against enemies. He might also be secretly glad that Frieza, his long - time enemy, is now in a form that he can tolerate (barely).
Another possible main character could be the villain that forces the two Gokus to meet. This villain could be a new, super - powerful threat that the two Gokus need to deal with. Their meeting becomes a crucial part of the story to defeat this powerful foe.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
Gohan would be really surprised, but being the kind - hearted person he is, he would try to understand and help out. He could offer to train with them in a more gentle way to keep them fit during the pregnancy. Piccolo would be more of a silent observer, but still be there in case of any threats.
The reaction among fans would be quite mixed. Some die - hard fans of the original series would be appalled as they have a clear image of ChiChi and Goku's relationship. They would see this type of fanfiction as a perversion of the original concept. On the other hand, there are those who are more open - minded and might see it as an interesting, if not controversial, exploration of the characters. But overall, the negative reactions would probably outweigh the positive ones.
Goku would be a mix of angry and worried. His Saiyan blood would make him want to rush into battle with Raditz right away. But he also knows how dangerous Raditz is, so he might first try to gather some allies, like Piccolo. He'd be constantly thinking about Gohan and how to rescue him as quickly as possible.