Cyrus (Cylon)
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Cyrus, or Cy, is a Cylon Centurion that is rebuilt by Starbuck to keep him from being lonely after he is separated from the Colonial Fleet. At first, Cy attempts to kill Starbuck, but the Colonial Warrior's charm (and weapons) help Cy to change his mind.
Cy fights off other Centurions to buy time for Starbuck's makeshift rescue boat to leave the planet with Angela and her unborn child. The robot, understanding the concept of friendship, sacrifices himself to save Starbuck (The Return of Starbuck).