After Raditz kidnaps Goku's young son, Gohan, Goku and Piccolo form a reluctant alliance in order to fight for a common cause but Goku sacrifices himself to help Piccolo kill Raditz.
After a minor conflict against a Bear Thief, Goku and Bulma returned the turtle back to the ocean where his owner, Master Roshi, gave Bulma his Dragon Ball and Goku the Flying Nimbus as a reward.
Another member, Oolong, joined when Goku and Bulma saved Aru Village; although Bulma actually forced him to go.
Afterwards, the team parts ways for another five years; during which time, Goku and Chi-Chi marry and give birth to their first son Gohan.
The first actual formation of the "Z Fighters" is out of necessity; brought on when Goku is faced with his long lost older brother Raditz, who had come to Earth to find Goku and tells Goku the truth about his Saiyan heritage.
Goku Bulma Oolong (later retires)Yamcha (later retires)Puar (later retires)Krillin Master Roshi Piccolo (joins during Saiyan Saga)Tien Shinhan Chiaotzu (later retires)Yajirobe (later retires)Gohan Vegeta (joins during Namek Saga)Future Trunks (returns to alternate timeline)Trunks Goten Android 18 (joins after Cell Games Saga)Majin Buu (joins during Kid Buu Saga)Uub Pan Chi-Chi Ox-King Launch Android 8Mrs. Briefs Upa Bora Korin Fortuneteller Baba Grandpa Gohan Kami (merges with Piccolo)Mr.
Popo King Kai King Yemma Grand Elder Guru Nail (merges with Piccolo)Dende Android 16Android 17Mr.
They traveled past Mount Paozu and into Skull Valley where they met Turtle.
Bulma was originally against the idea of taking the turtle back to the ocean, but ended up tagging along with them since she was defenseless without Goku.
Members will act of their own accord at times, though most if not all have some sort of sense of justice (or eventually developed one) and will make drastic decisions to defend their home.
Throughout the years, the group consistently bolstered its ranks through the addition of former enemies and new heroes, and routinely overcame seemingly insurmountable opponents; always emerging victorious against progressively more powerful foes.
Later, while training with Master Roshi for the 21st World Martial Arts Tournament, Goku met his best friend Krillin, and also Launch.