Dr. Michael Gehabich is a character in the anime Bakugan Battle Brawlers. He is the grandfather of Alice Gehabich. Similar to how Alice can become Masquerade, he also has a negative split personality in the form of Hal-G, as whom he is seen as for the majority of his appearances in the anime. He first developed Hal-G when a large amount of negative energy from the Silent Core infiltrated his lab. After Naga was defeated by Drago, Hal-G left his body and Michael returned to his normal self.
He is first seen in Moscow with Alice, fixing the gate to New Vestroia. When he tests it by sending a Russian doll, it fails to teleport. He tries once more with a Gate Card and it teleports successfully. However, unknown to him or Alice, it sent thousands of Gate Cards into New Vestroia, one which is caught by Spectra and given to Professor Clay. Later, Michael used the technology of Lync's gauntlet to fix the gate thus preventing Alice, Runo, and Julie from going to New Vestroia along with Dan and Baron, as they did not have gauntlets which were required to be able to enter.
Later, Klaus von Hertzon reveals that he worked with Dr. Michael in rebuilding the dimensional transportation by funding the project and to mass-produce the device. This explains how Klaus made it to and settled in on Vestal.
As Alice and Michael have the same last name, it is assumed that he is Alice's paternal grandfather.