List of Recurring Alien Characters in Stargate SG-1 - Replicators

The Replicators are a potent mechanical life-form using a quiron-based technology composed of building blocks using nanotechnology. They strive to increase their numbers and spread across the universe by assimilating advanced technologies. They are hostile to all other life-forms in the universe, but are opposed primarily by the Asgard. In the episode "Unnatural Selection", the Replicators had developed human-form Replicators, based on the technology they extracted from their Android creator, that appear just like humans and are able to change their form. Standard Replicators are resistant to energy weapons, and can only be destroyed by projectile weapons. Human-form Replicators, on the other hand, are resistant to projectile weapons as well due to the change in their nature from large blocks to smaller units the size of organic cells (cell blocks). In the episode "New Order (Part 2)", an Ancient weapon called the Replicator Disruptor was developed by O'Neill while he still had the knowledge of the Ancients in his mind. It works by blocking the cohesion between the blocks that make up the Replicators. The Replicators in the Milky Way galaxy were wiped out by the Dakara Superweapon in the two-part episode "Reckoning" at the climax of Season 8. It has been indicated that the Asgard used the same technology to defeat the Replicators in their own home galaxy as well.

• Fifth, played by Patrick Currie (seasons 6, 8) – A human-form Replicator introduced in season 6's "Unnatural Selection". He is the fifth human-form to be created on the Asgard planet Halla, and unlike the others he lacks the programming flaws of the android Reese, on which the human-forms are based. This makes him more "human" than the other Replicators, who consider him "weak" as a result. After SG-1 is captured by the Replicators, Fifth becomes fascinated by them, especially Carter, and attempts to help them, but SG-1 break their promise and leave Fifth behind in a time dilatation field. Fifth has escaped the time dilation field in the season 8 episode "New Order", and en route to the new Asgard homeworld of Orilla, he captures Samantha Carter and tortures her in revenge. He eventually relents when she appeals to his humanity again, and professes his love for her. He lets Carter go but creates a Replicator duplicate of her to serve as his consort. Fifth appears for the last time in "Gemini", conspiring with Replicator Carter to obtain data from the SGC that would immunize them from the Replicator Disruptor. Replicator Carter however never returned his feelings, believing him unfit to command the Replicators. She ultimately betrays him, taking the data for herself while manipulating him into being destroyed by the Disruptor. • Patrick Currie had auditioned for the show since the very beginning, resulting in approximately 15 auditions before being cast, according to Currie because the producers always short-listed him and waited for the perfect episode to use him in. When preparing for the role of Fifth, Currie was unsure where to take the innocence and vulnerability of the character, and later figured that the key to this character is to know "what it's like before we learn to play games and pretend". He thinks Fifth is a misunderstood character and not a villain; Fifth believes to love Carter, but lacks comparisons.
• Replicator Carter (also known as RepliCarter), played by Amanda Tapping (season 8) – A human-form Replicator created by Fifth. She first appears at the end of "New Order", and becomes a major adversary in the eighth season of the series. Fifth intended her to be a duplicate of the real Samantha Carter, but one who would return his affections. Replicator Carter seemingly defects from Fifth to the SGC in "Gemini", but in fact abandons him to be destroyed while she develops a means to immunize herself from the Replicator Disruptor. In "Reckoning", Replicator Carter launches a full-scale invasion of the Milky Way and personally eliminates the last of the Goa'uld System Lords. She abducts Daniel and probes his mind to find the location of the Dakara superweapon, the only thing in the galaxy capable of stopping her. She also sends Replicators to fight the forces of Ba'al, the Jaffa Rebellion, and Stargate Command on Earth. Daniel Jackson is able to exploit his connection to the Replicator network at a critical moment, buying enough time to finish calibrating and activating the Dakara weapon. The resulting energy wave breaks Replicator Carter and all her brethren into their constituent parts.