High Quality Content by WIKIPEDIA articles! In the military science fiction series Stargate SG-1, the Replicators are antagonistic self-replicating machines that propagate by ingesting the metals that make up civilizations and use them to create either blocks that form the bug-like version or smaller cells that compose the human-form "Replicators". They were first mentioned indirectly in the season 3 episode "Fair Game", and first seen onscreen in "Nemesis". In the show, the Replicators are primarily the enemies of the Asgard race, however, they act like a plague against all life thus, in the series, Earth must also contend with them on several occasions. The Asurans in the spin-off series Stargate Atlantis might be related to those in Stargate SG-1 as they are essentially human-form "Replicators".