In the military science fiction series Stargate SG-1, the Replicators are self-replicating machines that seek to convert all civilizations into more of themselves, thus posing a dire threat to all other beings. They were first mentioned indirectly in the season 3 episode , and first seen onscreen in . The Replicators are primarily the enemies of the Asgard race, but Earth must also contend with them on several occasions. The Asurans of Stargate Atlantis are also called Replicators, due to their similarities to the race on SG-1, but are not directly related.