Michael Shanks actually voiced two roles in Stargate SG-1. Best known for playing archaeologist turned galactic adventurer Daniel Jackson, Michael Shanks is virtually synonymous with the Stargate franchise. His character was introduced in the first Stargate movie, where Daniel proved to be the only one who could translate the runes inscribed on the Stargate dial. He returned in Stargate SG-1 as a member of the project's elite team, paying the ultimate price for his heroism: Daniel Jackson died in Stargate, only to ascend to a higher plane of existence and then return.
Shanks played another notable character in Stargate SG-1, though - or, rather, Shanks voiced him. He voiced the character Thor, the Supreme Commander of the Asgard fleet, one of humanity's greatest allies. The Asgard are one of the oldest races in the galaxy, the origin of humanity's tales of alien "little gray men." The aliens were actually puppets, with different actors providing the voice, and Shanks voiced Thor from his introduction in Stargate SG-1 season 2.
Why Thor & The Asgard Were So Important To Stargate SG-1
The Stargate project was tasked with traveling the galaxy, seeking technology that could be used to help them in their war against the Goa'uld. Over 10 seasons, Stargate team SG-1 sought out technologically advanced allies, but more were unwilling to help. They feared humans would abuse the technology they provided, and they refused to share their secrets. The Asgard, however, were the exception: they swore to protect Earth, and ultimately they allied with humanity, even helping provide the science to travel across galaxies. Without the Asgard, the Atlantis team would have been trapped in the Pegasus Galaxy, with no chance of ever being helped. In turn, Earth proved a capable and competent ally to the Asgard, helping them against the Replicators. The two races became close friends, and Thor stood at the center of this friendship.
Michael Shanks Played Thor Even After Daniel Jackson's Death
Michael Shanks left Stargate SG-1 in season 5, with Daniel Jackson ascending to a higher plane rather than dying of horrific radiation poisoning. Shanks actually voiced the part of Thor in a later episode titled "Revelations," the last episode where Shanks was listed as part of the main cast until season 7. Although Daniel Jackson himself didn't appear, the episode ended with a mysterious breeze, intended as a subtle hint Daniel was not gone after all.
Shanks seems to have been unhappy with the direction Daniel Jackson's arc was taking, but he couldn't stay away from his Stargate family. Daniel Jackson returned several times in Stargate SG-1 season 6, helping his friends despite the rules that were supposed to bind him. Still, despite playing both Jackson and Thor, Shanks' absence means he is not the actor to appear in the most Stargate SG-1 episodes; that honor goes to Christopher Judge, who played Teal'c. Amanda Tapping, meanwhile, continued with the franchise even after Stargate SG-1 had wrapped up, moving on to Stargate Atlantis.