Bakugan Gundalian Invaders

Bakugan Battle Brawlers (爆丸バトルブローラーズ, Bakugan Batoru Burōrāzu?) is a Japanese action adventure anime television series produced by TMS Entertainment and Japan Vistec under the direction of Mitsuo Hashimoto. The story centers on the lives of creatures called Bakugan and the battle brawlers who possess them. Though initially a failure in Japan, the series became popular in the United States and Canada, prompting the creation of a second season, New Vestroia, which aired in other countries before Japan. The third season, Gundalian Invaders, is currently broadcasting in the Canadian and US markets.

In the parallel world of Vestroia, a powerful Bakugan in search for power (a small marble magnetic sphere which when thrown on a gate card turns into a highly strong and powerful warrior) named Naga decides to absorb the energy of the two opposing cores that preserve the balance and peace in Vestroia. However he absorbed too much power and energy found within the Silent Core, the source of negative energy. The Infinity Core, the source of positive energy had been absorbed by Wavern.

In the first season, the story centers on six friends who find metallic cards which have fallen from the sky or to be more precise, Vestroia itself. They name themselves the Bakugan Battle Brawlers and consist of seven children: Dan, Shun, Runo, Marucho, Julie, Alice, and later Joe. Together they learn more about the origin of the Bakugan, Vestroia, the game involving them, and the battle against the Doom Beings.

In New Vestroia, Dan, Marucho, and Shun are called to the newly restored Vestroia to stop an alien race called the Vestals who invaded it. They allied with the Bakugan Battle Brawlers Resistance: Mira, Ace, and Baron in order to stop an evil group as the Vexos from taking over New Vestroia, and possibly, the whole universe.

In Gundalian Invaders, Dan, Marucho and Shun get caught up in a war between two different alien factions in another universe, and teaming up with three new brawlers, Princess Fabia, Jake (who is from Earth), and Ren (who is an undercover Gundalian) in order to stop the evil Gundalian Protectors, the Twelve Orders from destroying Neathia, and possibly, Earth.

Source: Wikipedia