Ten years passed since the end of Dragonball Z. Ubuu trains with Gokou. Goten and Trunks are adults. Pan is 14 years old. Satan is balding. Kuririn has a mustache and gray hair. Since the defeat of evil Buu, there was peace on earth...
Pilaf has finally gathered all the dragonballs to wish for world domination. Shenlong is summoned. Without notice, Gokou enters the scene. Pilaf, surprised to see Gokou after all these years, starts to wish that Gokou was still a kid so that he could be easier to defeat. Shenlong takes this for the wish and turns Gokou back into a kid. Pilaf runs off again and is never seen again.
Gokou returns to his house and tells about what happened. Popo appears and tells Gokou that there are Black Star Dragonballs scattered in space. Gokou decides to find these dragonballs to restore himself to his normal form. (The dragonballs of the Earth can only be used to grant wishes once a year.) More surprisingly, Popo tells that these Dragonballs must be gathered within a year or the Earth will explode! Gokou and Trunks get on a space capsule to set voyage on their new quest. Pan sneaks aboard the capsule and accidently damages an engine.
The space capsule crashes into many planets. In these planets, our heroes acquire the Dragonballs and meet a cast of minor characters. (It was these boring scenes that made people hate Dragonball GT at first.) During these scenes, Gokou and Trunks enter their Super Saiyan form for the first time in Dragonball GT to battle the minor villains. Pan also fights, but spends most of her time watching the Super Saiyans in amazement. In addition, our heroes meet Gill, a little robot who swallowed the Dragonball radar. As a result, our heroes take him on their journey.
Our heroes land on Dr. Myuu's planet. Dr. Myuu is an evil scientist who creates a bunch of cyborgs and robots. Gill is one of his creations. Trunks is kidnapped. Pan tries to rescue Trunks while Gokou fights Ruudo, a creation of Dr. Myuu. Ruudo is killed. Gill helps Trunks and Pan escape and our crew returns to space.
One of Dr. Myuu's project is Bebi. Bebi is really the only surviving Tsufuru-jin. Planet Plant, his native planet, was destroyed by the Saiyans back when the Saiyans worked as mercenaries for Freeza. As the only survivor, Bebi wants revenge on all Saiyans, innocent or guilty. Dr. Myuu found Bebi in space and saved him. Bebi has the power to take over bodies and acquire his victims' power. Bebi takes over Dr. Myuu's body and kills him in the betrayal.
Gokou, Trunks, Pan, and Gill finally return to Earth with all seven Black Star Dragonballs. Gokou takes them to Popo to secure them for later use. However, Bebi also lands on Earth. Slowly, he takes over the bodies of Trunks, Gohan, and Goten. Even when he leaves their bodies, an egg is left in their brain. This egg makes its victim a zombie of Bebi. (When Gohan was Gohan-Bebi, he fought and injured Piccolo with a fireball.) Bebi finally finds a body that satisfies him- Vegeta's! Vegeta's body is taken over and Bebi-Vegeta is formed! Soon, everyone on Earth become zombies of Bebi except Satan, Pan, Buu, Ubuu, and Gokou. Popo, also a victim of Bebi, uses the Black Star Dragonballs to creat another Planet Plant for Bebi.
(By this time, Dragonball GT began to get interesting and unsatified fans began to take up interest in this sequel series to Dragonball Z.)
Ubuu faces Bebi-Vegeta and is defeated. Fat Buu joins the battle and is killed. Buu's body is near Ubuu and his spirit enters Ubuu. The two fuse and Ubuu learns that he and Buu were originally one. However, even with this fusion, Ubuu is no match for Bebi-Vegeta.
Gokou faces Bebi-Vegeta. Bebi-Vegeta is stronger and easily defeats the young Gokou. Gokou powers up to Super Saiyan level 3, but is still defeated; Bebi-Vegeta can also power up to level 3. Pan hides in the background and watches the fight. The defeated Gokou is pulled out of the fight by Kaiou-shin. On Kaiou-shin's planet, the Kaiou-shin inhabitantsubstances are creating a formula that will make Gokou's tail grow back. (The tail is the main source of power for a Saiyan.) Gokou's tail is only partially grown. Kaiou-shin pulls it to make it reach normal length.
Gokou returns to planet Plant to face Bebi-Vegeta. After getting beaten by Bebi-Vegeta again, Gokou lies on the ground and stares at the Earth. The "full-Earth" acts as a full-moon. As a result, Gokou reaches Oozaru stage and becomes a giant golden ape. (The ape is gold instead of brown because it was the Earth that caused the transformation instead of the moon). Gokou is a lot stronger, but is unable to control his body in Oozaru stage and trashes everything in sight. Another change occurs. Gokou acquires control over his body and enters another stage beyond Oozaru. He powers up and becomes Super Gokou 4. The tide of the battle is turned and Bebi-Vegeta is losing. The zombie Bulma creates a special magnifying glass for her husband. It magnifies the rays of the full-Earth and Bebi-Vegeta enters Oozaru stage.
Gokou gets defeated once again. Meanwhile, Kaiou-shin resolves that Chou-sui water could cleanse people from Bebi's control. He goes to Sky Palace to get the Chou-sui water. Dende and Popo are cleansed in the struggle against Kaiou-shin. This water is spread to everyone. Gohan, Goten, Trunks, (now free from Bebi's control) and Pan surround Gokou and form a circle. Their energy is donated to Gokou. Gokou and Bebi-Vegeta face each other again. Gokou does a Kamehameha fireball and defeats Vegeta-Bebi. Bebi leaves Vegeta's body and runs to a space capsule to escape, but is killed.
The Earth is about to explode because the Black Star Dragonballs weren't used to wish for the Earth's stability. Our heroes fly all the inhabitants to planet Plant. Piccolo decides to stay on Earth to die with it because he loved it so much. (He is still injured from the blast from Gohan-Bebi.) The Earth explodes, and Piccolo goes with it. At The Namek Dragonballs are gathered and the Earth is restored from the wish, but Piccolo is still dead. However, one thing is learned- Gokou reached a new stage as Super Saiyan...