Fifth was the fifth of the Replicators to evolve into human form within the time dilation bubble on Hala. As a human-form Replicator, Fifth was impervious to projectile weapons, and was capable of reaching into the mind to read one's subconscious thoughts. The programming of the android Reese was used as the model for the human-form Replicators, but a flaw in her emulation program was discovered during the creation of First, and an attempt was made to correct the error during the creation of Fifth. The correction gave Fifth compassion, which was seen by the Replicators as a weakness that would not be repeated. Fifth was betrayed by his own humanity when he agreed to help SG-1 reconfigure the time dilation device and escape if they promised to bring him with them. However, he was left behind as the device activated, and was trapped with the others in a time dilation field.
Although the Asgard attempted to eliminate the Replicator threat by drawing the planet Hala into a black hole, Fifth escaped, captured Carter by bringing her aboard his ship, and headed for the Asgard planet of Orilla. He claimed that his humanity gave him an advantage over the other Replicators because it allowed him to experience cruelty, betrayal, and revenge. Reaching inside Carter's mind, he used torture and mind control to convince her that she had left the stargate program and was now living a peaceful existence on a farm in Montana with Pete Shanahan. Carter rejected Fifth, but his conflicted feelings of love and the desire for revenge would not allow him to kill her, and in an act of compassion he left her behind on Orilla when he and his brethren escaped. Instead, he created a new human-form Replicator in Carter's image.
Bent on revenge, Fifth and his Replicator brethren entered the Milky Way galaxy, knowing that the SGC's disruptor technology was the only weapon that could stop him, and he sent Replicator Carter in advance to seek a cipher that would render the disruptor ineffective. However, Replicator Carter saw her creator as weak and unworthy, and once again Fifth was betrayed when Replicator Carter cooperated with SG-1, isolated the cipher that would make her immune to the disruptor, then fired the weapon herself against her creator. Fifth and his ship were instantly destroyed, and Replicator Carter ruled the Replicators in his place.
Portrayed by: Patrick Currie