Stargate: 10 Best Aliens In One Episode Only
7. P3X-118 Foothold Aliens
This race of aliens manages to successfully infiltrate the SGC, using their mimetic technology. They can appear as any captured soldier that they have connected to their hive mind, which is bad news for Carter when she tries to convince, of all people, Maybourne of the invasion situation.
They speak about the Goa'uld being 'the dominant parasitic life in the galaxy', suggesting that they are originally not from the Milky Way galaxy, even though they gained access by impersonating SG-6 and coming through the gate.
Though the aliens are not seen again after these initial soldiers self-destruct upon their discovery and defeat, their technology means that they could impersonate anyone that they capture, down to every strand of hair on that person's head. These are a race that seemed destined to return.