High Quality Content by WIKIPEDIA articles! Ruby is a fictional character on The CW Television Network`s Supernatural portrayed by Katie Cassidy and Genevieve Cortese. Created by the writers in order to expand on the characterization of demons within the series, she first appears in the third season, rescuing Sam and Dean Winchester, and continues to assist them throughout the season. By the fourth season, she has won Sam`s trust and begins training him to kill demons with his powers, though Dean remains fearful of ulterior motives. Due to budgetary reasons, Katie Cassidy was replaced by Genevieve Cortese after the third season, and the character departs the series at the end of the fourth season. Though the fans reacted negatively towards the character at first, Cortese and creator Eric Kripke felt that they became more accepting of her as the fourth season progressed.