After drinking the Ultra Divine Water, Goku has a rematch against King Piccolo to take revenge on the deaths of Krillin, Master Roshi, Chiaotzu and all other people killed by the Demon King and his servants. Goku shows power beyond that of King Piccolo who knows that the only chance for him is to go to full power. When the battle gets tough, Goku knows that he needs to do an all or nothing attack. He breaks through the Namekian's stomach killing him, however, he spits out an egg containing his final son, Piccolo Jr.
If the transformation button isn't pressed during the battle then the dialogue will still be the same at the end of battle. If it is pressed once but King Piccolo is beaten before the next one appears then Tambourine will appear after somehow surviving Goku's Kamehameha. Chi-Chi then appears and finishes the demon off.