Role in the anime
Dr. Michael Gehabich has accidently sent to Vestroia and encounters Naga, a Dragonoid, he was cursed by Silent Core's negative energy by this rogue Bakugan caused to turn him evil.
Naga and Hal-G has created the Doom Cards to manipulate the brawlers into sending the fallen Bakugan to the Doom Dimension for Masquerade who wants to evolve Hydranoid to take over the world.
Near the end of season 1, he was expelled from Michael's body following Naga's death at the hands of the protagonist Drago and their friends.
He was never seen again since his defeat.
It is rumored if Hal-G will appear in Bakugan Reboot as the hidden antagonist or major antagonist.
Hal-G shares similiarities with Mal
Both of them are the clones of the hero
Both of them take over the protagonists' minds