Kitty Canary, aka Carla Breezer (Lisa O'Hare), is the main villainess from Castle's third season opener, "A Deadly Affair" (airdate September 20, 2010). She is the owner of a burlesque club and the girlfriend of Earl Moreland.
Kitty's brief backstory revealed that she served five years in prison for attempting to run over her previous boyfriend in Seattle, where she worked as a stripper. After her release, she headed to New York, where she met Earl, and began running her burlesque club. To solve their financial woes, the couple colluded with Chloe Whitman and Maya Santori to start a counterfeiting ring, but their business was in jeopardy when Todd McCutchin used the counterfeit bills to pay off a loan shark. The shark ended up learning about the ring and threatened to rat out Todd unless he turned over the operation.
Maya and Chloe were willing to turn over the operation, but not only were Kitty and Earl unwilling, the former enlisted the latter to kill their cohorts, which Earl does by shooting them to death. Richard Castle was found near Maya's body, leading to his arrest, but he was quickly cleared. Meanwhile, the evil Kitty sent Earl to kill Todd as well, and in the episode's climax, the couple was shown packing up their materials and planning their escape, as they figured that they would be exposed following their encounter with Castle and Kate Beckett. It was at that moment that the duo appeared with Ryan and Esposito, as they had figured out that Kitty and Earl were the killers. This led to a shootout between the couple and police, which ended with Beckett and Castle (non-fatally) shooting Earl and Kitty, respectively, before the couple was arrested.