"Dragonball GT" is the anime-only continuation of the "Dragon Ball" franchise, not endorsed by Akira Toriyama; this series follows Son Goku's later adventures after an errant wish reduces him to a child. He ends up facing Bebi, a villain from Planet Plant, Super 17, a character from the afterlife and the seven Shadow Dragons created by corrupted energy from the Dragonballs. "Dragonball GT" is considered non-canon with the release of "Battle of Gods" and "Revival of Freeza."
"Dragonball GT" starts with Goku and Uub, the reincarnation of Buu, training in the Room of Spirit and Time. They are disturbed by an old villain Pilaf, who accidentally makes a wish to turn Goku into a child again. The wish was made on the Black Star Dragonballs, which thereafter scatter throughout the universe and have to be returned in a year. Goku, his granddaughter Pan and Vegeta's son Trunks journey through space and gather the Dragonballs.
They encounter Bebi, who comes to Earth with the intent of reviving his home planet. He possesses Vegeta, and Goku reaches the form of Super Saiyajin 4. After Bebi is defeated, Super 17 escapes from the afterlife. The wish made to undo the damage he caused releases the seven Shadow Dragons. Goku, Vegeta and Pan fight the dragons one by one, finishing the last one with Goku's most powerful attack. Afterward, the Dragonballs vanish, and Goku leaves with the Eternal Dragon. The final scene is of Goku and Vegeta's descendants fighting in a tournament.