Like the others of the "Significant Seven", there are several versions of her, including Caprica-Six, Shelly Godfrey, Gina Inviere, Natalie Faust, Lida, and Sonja.

Several notable versions have had more prominent roles: At the beginning of the miniseries, a Six copy[5] is involved in an intense affair with Dr. Gaius Baltar.

Pretending to be an employee of a computer corporation, Six seduces Baltar while helping him with his work on the Colonial Defense System.

Caprica Six is enlisted to motivate the resurrected Galactica copy of Sharon "Boomer" Valerii to move out of her apartment and reintegrate into Cylon society.

The other Cylons insist Baltar must sign an execution order for 200 insurgents in response to two suicide bombings by the human resistance movement.

Caprica Six becomes involved in a ménage à trois with Baltar and Biers after settling on the Basestar and explicitly states she loves both of them.

While this briefly leads Baltar to think he has truly gone insane, he concludes this is impossible, given Six's knowledge of events unknown to him (for example, the prediction of the birth of the Human/Cylon Hybrid to Sharon Agathon while a prisoner aboard Galactica).

Confronted with this in Part II of "Home", Six declares that she is neither a computer chip nor a hallucination produced by mental instability.

While Six can physically interact with Baltar in his imagination, it is for most of the series unclear if she is able to physically affect him in the real world — this is finally resolved in the episode "Escape Velocity", where Head Six is shown lifting Baltar from the floor to a standing position after he endured repeated blows from a Galactica marine.

This belief is supported by the fact that Caprica Six has her own Head Baltar, implying some sort of transcendental connection between those two specific characters.

She and Head Baltar are the last-seen characters in the final moment of the episode, which takes place 150,000 years after the rest of the series.

[10]) This Number Six gains the confidence of Rear Admiral Helena Cain, with whom she has a romantic relationship, and then-Lieutenant Kendra Shaw, who gives Gina the administrator codes for the Pegasus mainframe.

Gina uses Shaw's password in order to disable the Pegasus during a Cylon attack, enabling the ship to be boarded by centurions.

Cain orders her former lover's imprisonment, condemning her as a thing, and allows Gina to be subjected to torture and gang rape by members of the Pegasus' crew.

In the two-part episode "Resurrection Ship," Gina comes out of her catatonic state completely and is so traumatized from her ordeal that she wishes to truly die.

The extensive sexual abuse she has suffered renders Gina psychologically unable to be intimate with Baltar until shortly before her death.

Presumably, this second Resurrection Ship was out of range as the Cylons had chosen to stop chasing the fleet at the time due to the efforts of Boomer and Caprica Six.

Gina helped prep Boomer for her upcoming transition to a sleeper agent and provided IT support for her cover identity.

[12] A Number Two from their damaged Baseship, Leoben Conoy, takes a Heavy Raider and manages to make contact with Lieutenant Kara "Starbuck" Thrace and her crew on the Demetrius, a sewage processing vessel repurposed for long-range exploration in the episode "The Road Less Traveled".

In the episode "Faith", Conoy, Thrace and some of the Demetrius crew take a Colonial Raptor to the rebel Basestar and make repairs, allowing the Baseship – the Demetrius following behind – to jump to the Colonial fleet in the episode "Guess What's Coming to Dinner", in which Natalie makes a deal with Rear Admiral Adama on the Galactica to reveal the location of the main Cylon Resurrection Hub and help the Colonials destroy it, ending resurrection for the enemy Cylons, as long as she can bring the "Final Five" with her off the Galactica after Earth is located.

Natalie is on her way to speak to Adama again when she encounters the human-Cylon hybrid infant Hera Agathon in the corridor and bends down to talk to her.

Her surname is not used onscreen, and her first name is only used once, by a Number Eight in the episode "The Hub", who notes that the Hybrid of their Baseship has reacted to Natalie being killed or injured on Galactica.

Michael Angeli's original version of the script for the episode "Six of One" has John Cavil refer to Natalie Faust by her full name and mention that she infiltrated Gemenon posing as a political reform advocate.

Sonja revealed that Number One, John Cavil had moved The Colony from its original location 5 months prior shortly before the Cylon civil war took place.

And in the series finale, she is seen along with a two and an eight discussing their plan with Adama on how to populate the new Earth saying that they'll stay alongside the humans in their new home until their own deaths come.

She had been a prostitute on the Colonies, and eventually drunkenly mocks John Cavil's schemes while sharing a bed with him, following the not-quite-fatal shooting of Commander Adama by Cylon sleeper agent Boomer and the suicide of their fellow infiltrator Simon O'Neill, a Number Four.

She points out that most of the Cylons' failings, including those mentioned above, along with Number Two Leoben Conoy's interaction with Lieutenant Kara "Starbuck" Thrace and Shelly Godfrey's failure to ruin Gaius Baltar, have been due to love, and leaves the room telling Cavil that "you can't declare war on love".

The ultimate fate of Tough Six is unknown, whether she was captured and executed or remained in the fleet until New Caprica, as she is not seen in The Plan following her exit from Cavil's bedroom and did not appear in regular episodes.

Number Sixes have been shown in a variety of roles, including repairing the Galactica ("Deadlock" and "Someone to Watch Over Me"), hospital administration ("The Farm"), serving as Heavy Raider pilots, and as rebel Cylon leaders (Natalie and Sonja).

[18] James Maddox of Game Rant wrote, "Tricia Helfer's seductive Number Six came to define the humanoid Cylon in pop culture and is in many ways the most iconic element of the franchise as a whole.