Stargate: SG1

The basic premise of Stargate Sg-1 is that a secret military team has discovered a network of portals that can instantly transport people all over the galaxy -- so, with typically earnest human curiosity, they set off to discover the mysteries of the cosmos. The show has a very complex mythology: The Stargates were created by the Ancients, an ultra-advanced race that disappeared eons ago, and humans and several other races are slowly figuring out how to use them. One of these is the Goa'uld, a snake-like species of parasites bent on taking over the galaxy; until the Stargate team arrived on the scene to oppose them, they were close to attaining their goal.