Complete list of Stargate SG-1 episodes featuring the Replicators

Stargate SG-1 Season 3:

episode 322: Nemesis (1)

Colonel O'Neill is abducted by the Asgard and beamed aboard the spaceship Belisker. Immediately O'Neill encounters bug-like robots known as Replicators.

Stargate SG-1 Season 4:

episode 401: Small Victories (2)*

Thinking that they have saved the Earth form the threat of the Replicators, the Startgate SG-1 team return to Stargate Command only to learn that a Russian submarine has been besieged by the persistent bug-like robots.

Stargate SG-1 Season 5:

episode 501: Enemies (part 3 of 5)

The SG-1 team have been accidentally thrown into another galaxy by a supernova where they encounter the Goa'uld System Lord, Apothis. However, Apophis has trouble of his own as he faces the Replicators.

episode 519: The Menace

The Startgate SG-1 team visit a planet that was one the home a a technologically advanced race, but the planet is now desolate. While exloring, they come across a preserved android and bring her back to Stargate Command. Major Samantha Carter figures out how to reactive the android, known as Reese, and eventually learn that Reese created the Replicators and has brought the Replicators to Earth.

Stargate SG-1 Season 6:

episode 612: Unnatural Selection (part 2 of Prometheus)*

The Asgard, Thor, solicits Colonel O'Neill to help the Asgard to defeat the Replicators once and for all. Thor suggests the Earth built spaceship Prometheus can fly into Replicator space unchallenged because its technology is not advanced.

Stargate SG-1 Season 8:

episode 801: New Order*

Colonel is in suspended animation in a newly discovered alien base under Antarctica on Earth. The Asgard, Thor, is still battling the Replicators on the planet Hala. When the Replicators are almost sucked into a black hole, they escape by invading Thor's shop where Captain Carter and Teal'c try to fight them off. Back on Earth, Stargate Command is trying to form an alliance with the Goa'uld System Lords but they are secretly scheming against Earth.