Altair (Stargate)

Many thousands of years ago the inhabitants of Altair retreated underground after the surface of their planet became uninhabitable. They eventually developed the technology to replace their bodies with android replicas and long since left the planet, through the Stargate, with the exception of one called Harlan.

After a brief encounter with Harlan, SG-1 returned to Earth, but subsequently discovered that their consciousnesses had been placed into exact android doubles constructed by Harlan, who was desperate for companionship and assistance with maintaining his subterranean facility. Unable to stray too far from the power source on Altair, SG-1 was forced to return to Altair and confront Harlan and demand restoration to their original bodies. Harlan reveals that their original bodies are in fact still intact, stored unconcious in a laboratory, and that their minds were copied rather than moved; he had intended to send the originals back through the Stargate later once he was sure the copies were stable without revealing their continued existence to the androids or vice versa.

The android duplicates decide to remain on Altair once their originals are rescued, not having any other choice due to their reliance on Harlan's power source and the impossibility of "restoring" them to their organic bodies. Unfortunately since they retained all the knowledge of their originals they knew they would be considered a security risk, so the androids decided to bury the Stargate after the original SG-1 team left to make Altair unreachable. They didn't remain isolated for long, though; the android SG-1 team soon dug the Stargate back up and began venturing through it themselves to secretly help correct problems their originals caused in their own travels to other planets. The android team eventually died in action in the course of defeating the System Lord Cronos, but Harlan survived and presumably remains in residence.