Development
The writers introduced Ruby in the third season to change the perception of demons into more of a grey area, rather than the "black and white", "They're evil, we're good" approach previously used in the series. Writer Sera Gamble commented, " brought the idea that you can't just dismiss demons as things that need to be killed right away. They could be useful, and while fundamentally untrustworthy, there might be cause to trust them in a given situation." Due to "protective and occasionally nervous" fans, series creator Eric Kripke meant to introduce Ruby in "small doses". Wanting fans to know the show would always be about Sam and Dean, and nothing else, he stated, " there for important plot elements, but it's not the Ruby and Bela show, nor is it about the four of them cruising around in the Impala together. It's about the guys." Therefore, Ruby was not introduced to be a love interest for Sam or Dean, but rather to be an antagonistic character.
When Katie Cassidy (who had originally auditioned for the role of Bela Talbot) joined the series, she had to train in kickboxing to be able to perform Ruby's martial arts skills. This prompted her to attempt as many of the fight scenes as she could, rather than rely on her stunt double. She also prepared by looking to Sharon Stone's performance in the film Basic Instinct for inspiration due to Ruby's manipulative ways. Because of her height difference with the lead actors—Cassidy is 5'7" while Jared Padalecki is 6'4"—she had to wear tall, spiky high heels that at times made her lose balance.
| “ | Rather than introduce some entirely new body for Ruby that'll get confusing for the audience and confusing for Sam, why not keep going back to a performance that we're loving? | ” |
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—Kripke on the decision to keep Cortese. |
Due to budgetary reasons, Cassidy was let go after the third season. To "make the best out of a bad situation", Kripke and the writers planned for Ruby to take on a new host every few episodes for the fourth season. They believed this would "keep guessing", and provide a "cool character that most shows don't have the ability to do". Genevieve Cortese played the first of what was expected to be many incarnations. To prepare for the role, she viewed DVDs of Katie Cassidy's portrayal. Cortese found it at first strange stepping into Cassidy's shoes, stating, "I was conflicted over where Ruby is now versus where she's come from." Taking from the third season finale in which Dean is sent to Hell, Cortese portrayed the character as having some guilt over his death. She also wanted the character to seem "as innocent as possible" to make viewers question her true allegiance. Impressed by the actress, Kripke chose to keep her in the role because she "brought a lot of the different colors and vulnerabilities to Ruby that was really looking for".
Read more about this topic: Ruby (Supernatural)