Ubb Character Facts

Uub is from a tropical island, and he grew up in a small village on the island. He is the oldest of five siblings, and he works hard to take care of his family who are starving and poor.
Uub when first introduced in the Kid Buu Saga, is very timid in his personality, despite his amazing power, becoming frightened at someone's slight expression. However, after training with Goku for many years, he becomes a confident fighter, wanting to make sure all evil is vanquished.
As a young boy, at the age of ten, Uub competes in the 28th World Martial Arts Tournament, which takes place ten years after the defeat of Kid Buu, wanting the prize money to help his family. It is revealed here by Goku that Uub is actually the reincarnated Human form of Kid Buu, and that he was born from the wish made by Goku just before Vegeta defeated Buu with Saiyan Spirit.
Uub actually has good intentions of entering the World Tournament; his plan is merely to attempt to win the prize money of 10,000,000 zeni in order to feed his starving poor village. Being the strongest from his village, Uub then realizes that there may be people in the world who are even stronger than him. With this, Uub loses hope, and becomes even more nervous when taunted by Nok.
Though Uub, the reincarnation of Kid Buu, was the most powerful human in existence, he still seemed to pale in comparison to that of a Super Saiyan. In a sparring match at the beginning of GT, Uub was just barely holding his own against his master and friend Goku, who was in his base form.
Majuub  is the result of the fusion between the innocent Majin Buu and Uub in Dragon Ball GT, which creates a much stronger and more muscular version of Uub, who wears Majin Buu's black and yellow vest. He also gained a massive boost in power, capable with keeping up with Baby Vegeta(Final Form). He makes his debut on the episode "The Return of Uub" Majuub retains many of Majin Buu's abilities, including the power to turn organic beings into chocolate (and possibly other kinds of matter if he wished).