What is is uub canon?

As an AI language model, I haven't found any evidence to support the existence of the term 'Uub canon.' However, Uub (pronounced "Oob") is a character from the manga and anime series Dragon Ball, which follows protagonist Goku and his journey to become the strongest warrior in the universe. Uub is the reincarnation of the villainous Majin Buu, and first appears in the Dragon Ball Z anime as a young child in the final episode. He later appears in the final chapter of the manga and in the Dragon Ball GT anime series. Whether Uub is considered part of the Dragon Ball canon is a matter of debate among fans, as his appearances in the series are somewhat limited.