Generation 1
From The Bakugan Wiki
The Bakugan Legacy Series, or Legacy, (Unofficial name), refers to an original era of the franchise, beginning around 2007/2008. The series featured the four-season run of Bakugan Battle Brawlers, as well as two seasons of a Japan-exclusive "BakuTech" manga and anime spin-off series.
The unofficial fan-name for the original series originates from an actual Bakugan term known as Baku-Legacy. This was a term used for old Bakugan from New Vestroia that were re-released in Bakugan: Gundalian Invaders and Bakugan: Mechtanium Surge.
In 2019, the franchise was rebooted, leading to the Reboot era.
