1 of 12 Justin Stephens/Sci Fi Channel
1) Cylon Model 3 first appeared as D'Anna Biers (Lucy Lawless), a reporter for the Fleet News Service. She boards Galactica "filming" a documentary about the military. But at the end of the episode, we see the Cylons watching the footage with D'Anna.
2 of 12 Carole Segal/Sci Fi Channel
2) Aaron Doral (Matthew Bennett), or Model 5, first appeared as a civilian public-relations specialist prior to the Cylon attack on the colonies. With the help of Gaius Baltar's hallucinations, he outed Doral as a Cylon.
3 of 12 Justin Stephens/Sci Fi Channel
3) "Six," aka Shelly Godfrey, Gina, Caprica (Tricia Helfer), has seen a lot of action on BSG. "Six" helped destroy Caprica and also saved Gaius Baltar from the nuclear holocaust. He now often interacts with his hallucination of her.
4 of 12 Carole Segal/Sci Fi Channel
4) Leoben Conoy (Callum Keith Rennie) was tortured by Starbuck early in the series, and then he got to return the favor on New Caprica by holding her hostage and making her believe she had a daughter.
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5) Sharon "Boomer" Valerii (Grace Park) was a frakkin' great pilot before she shot Admiral Adama in front of the entire ship. After her Cylon copy "Athena" became pregnant with Helo's baby, she swore her allegiance to the humans. But will it last?
6 of 12 Carole Segal/Sci Fi Channel
6) Simon (Rick Worthy) conducted hybridization experiments on Starbuck on Cylon-occupied Caprica.
7 of 12 Carole Segal/Sci Fi Channel
7) Cavil (Dean Stockwell) was revered as a colonial brother and a lay clergyman, until he was brought face-to-face with his Cylon copy.
8 of 12 Carole Segal/Sci Fi Channel
8) Col. Saul Tigh (Michael Hogan) is probably the most stunning addition to the group. A rabid Cylon-hater, he's spent 30 years trying to eliminate the toasters. He even killed his wife when he discovered she was a Cylon collaborator. Awkward!
9 of 12 Carole Segal/Sci Fi Channel
9) Chief Galen Tyrol (Aaron Douglas) not only discovers he's a Cylon, but realizes that his son with Callie is a now a human-Cylon hybrid.
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10) Sam Anders (Michael Trucco) already had to deal with his separation from Starbuck, then her supposed death, and now has to deal with the fact that he's a frakkin' Cylon! The honeymoon is so over.
11 of 12 Carole Segal/Sci Fi Channel
11) Presidential aide Tori (Rekha Sharma) has been Roslin's right-hand woman through thick and thin, and was stunned to learn of her true nature. Talk about keeping your friends close and your enemies closer!
12 of 12 Justin Stephens/Sci Fi Channel
12) Our guesses Baltar (James Callis): Because he sees visions of Cylons. Starbuck (Katee Sackhoff): Because she blew up, but then reappeared alive two months later. Apollo (Jamie Bamber): Because that would be seriously frakked up.