Stargate SG-1 1x10: "Thor's Hammer": While it doesn't quite introduce the Asgard as we will know them in the future, this episode does introduce the concept of a powerful alien race with the technology to counter the Goa’uld. And that would become rather important to the series as a whole. That said, this episode itself is a little slow, especially in the second act, but I like most of the ideas at play. #StargateSG1