Other breeds are possessed by the Orbanians who use them in selected children to collect and store information until, following the Averium of Urrones, they are extracted from them and one is deposited into every member of the Orbanian population. The Orbanians have been using this technology circa 1950's Earth.
The Replicators evolved beyond the crude block form to become a life form made up entirely of self-replicating nanite cells. These human-form Replicators are able to change forms, penetrate living tissue with a touch, and resist traditional weapons fire because of their nanite structure.
Brief Candle - O'Neill finds nanites have infiltrated his body and are accelerating his metabolism at an alarming rate.
Learning Curve - The S.G.C. discovers a culture which thrives on gaining knowledge and storing it within nanocytes.
Proving Ground - The S.G.C. conducts a training simulation in which nanites are used to help cover the true purpose of the mock foothold.
Unnatural Selection - SG-1 encounters Replicators who have taken human form, made up of trillions of microscopic nanites rather than large, bulky blocks.
The Real World - Dr. Weir's body and mind are taken over by Replicator nanites, after she is infected by Niam.
Adrift - McKay and Dr. Keller reprogram the inert Replicator nanites in Dr. Weir's system to heal her body -- leaving her permanently reliant on the nanites to live.
Lifeline - When the team infiltrates the Replicator homeworld, Weir uses her newly functioning nanites to access their wireless system and guide the team to safety -- and to control Oberoth and the other Replicators who threaten the team.
Miller's Crossing - Jeannie Miller gets injected with some prototype Earth-made nanites, but they don't work properly.
Be All My Sins Remember'd - Rodney McKay uses the Ancient technology that originally created the Replicators to create a new being, a "Friendly Replicator Android."