In the 2004 Battlestar Galactica, Tricia Helfer played the humanoid Cylon model designated Number Six.
Number Six is not just one individual but a model line with numerous Cylon copies. Helfer portrayed several distinct Sixes, including Caprica-Six, Shelly Godfrey, Gina Inviere, and Natalie Faust. Each copy could develop different experiences and loyalties while retaining the model’s recognizable appearance and core traits.
Sixes were part of the humanoid Cylons capable of convincingly imitating humans. Like other humanoid models, they could be downloaded into a new body after death, allowing the Cylons to preserve memories and personalities. Caprica-Six’s role in infiltrating the Colonies makes the model central to the series’ opening catastrophe.
Number Six is sometimes confused with Number Eight, the model associated with Sharon “Boomer” Valerii and Sharon “Athena” Agathon. Number Three, or D’Anna Biers, and Number One, John Cavil, are separate Cylon models.