In the exciting new season of Bakugan, the VESTROIAN star system is made up of six planets each home to a different species of Bakugan. 
Experimental weaponry causes the Bakugan to be transported to Earth, where humans welcome them, until teenagers start pairing with Bakugan and gain the ability to grow to giant size; during this time filled with fear, the Catastrophe takes place. 
(Source: 9Go!)

The Bakugan battle brawlers began when two young boys by the name of Dan and Shun made the rules to a mysterious game played with bakupearls, gate cards and ability cards. No one would ever have guessed what was going to happen next as Dan and his new internet friends battle their way to the bitter end.

When Bakugan began emerging from the earth's crust in a mysterious worldwide "awakening," Dan and his friends find themselves at the epicenter of a new age. Dan and Company quickly learn that they must grow into more than just suburban kids looking for quick fame in the post-Bakugan era. They must learn how to work with their Bakugan and deploy them in battle in order to survive the seemingly endless forces out to control, enslave or just plain destroy the mysterious race of alien creatures. Dan and his friends will evolve into bona fide heroes by protecting their Bakugan, the Earth and ultimately the incredible secret hidden beneath our feet: Our planet has merged with another, living planet Vestroia. (Source: Anime News Network)

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