Erica Hahn, who made an appearance in the second season but moved to Seattle Grace in the fourth season, is a cardiothoracic surgeon who was a fierce rival of Preston Burke's when they both attended Johns Hopkins Medical School. She had previously worked at Seattle Presbyterian Hospital across town. Erica had a tense relationship with Cristina Yang because she consistently denied Cristina the opportunity suck up. Erica formed a particularly notable relationship with Callie Torres. Erica presents herself in a confident and isn't afraid to speak up for something she believes in