 The season four premiere introduces several new interns , to be trained under Meredith , Yang , Karev , Stevens , and eventually O 'Malley . Among them are Dr. Steve Mostow ( Mark Saul ) who continues to make appearances , and Dr. Sadie Harris ( Melissa George ) who formed a friendship with Meredith while the two were in college . Harris is fired in the fifth season , due to not actually having a medical degree , and departs the show immediately after . Meredith and Shepherd 's relationship reaches a toll , and the two separate , leading Shepherd to entertaining a relationship with Rose ( Lauren Stamile ) , a nurse . Rose appears frequently until season five , when Shepherd rekindles his relationship with Meredith . Throughout the fifth season , Stevens experiences full @-@ out hallucinations of Duquette , signaling that she is ill , and once she is lucid , he departs , marking his final appearance . Following the announcement of her relationship with Robbins , Callie 's father Carlos Torres ( Hector Elizondo ) initially contests his daughter 's concurrence in homosexuality , but eventually accepts it , and he reappears several times throughout the series . 
