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.
In a Goku Naruto crossover, both characters have their own strengths. Goku's physical strength and energy attacks are off the charts. His ability to instantly teleport and sense ki gives him an advantage in combat. Naruto, though, has a unique power system. His connection to the Nine - Tails and his ability to use different types of chakra make him a force to be reckoned with. If we consider a battle, Goku's power might seem greater on the surface. But Naruto has the advantage of being able to surprise his opponents with his ninjutsu and clones. Also, Naruto has a strong willpower that has allowed him to overcome many tough situations, which could play a role in a fight against Goku.
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.
Vegeta from the Dragon Ball series is often popular. Fans like to write about his reaction to Naruto's world and how he might interact with the characters there. Also, Sasuke from Naruto is frequently included. He could be a rival or an ally in the fanfiction, given his complex character. Another one could be Piccolo. His calm and strategic mind would be interesting to incorporate in stories involving Naruto's more chaotic ninja world.
Their relationship could develop in a very interesting way. Given Naruto's background of being an outcast in his village at first, he might be a bit hesitant to fully embrace Goku as a brother. But Goku's open - heartedness would gradually break down those barriers. Goku would introduce Naruto to his friends in the Dragon Ball world, and Naruto would do the same in the ninja world. They would start to share their stories, like Naruto's fight against Pain and Goku's battles against Frieza. Through these shared experiences, they would grow closer and closer, until they are inseparable brothers who are ready to take on any threat to their combined worlds.
Naruto's ability to use chakra could give Goku a new way to power up. Maybe Goku could learn to combine chakra with his ki, creating a whole new level of power. Also, Naruto's shadow clone jutsu could be used by Goku in his training, allowing him to fight multiple opponents at once and improve his skills faster.