Introduced near the end of Season Two as the love interest of George - and now his wife - this orthopedic surgeon is not afraid to ruffle the interns' feathers.
Dr. Calliope "Callie" Torres first appeared in episode the "What Have I Done to Deserve This?" She met George when treating him for a dislocated shoulder, which he suffered falling down the stairs... fleeing Meredith.
While she appears to be a strong woman on the surface, Calliope clearly has her insecurities. She grew defensive after being criticized by Izzie for not washing her hands after using the bathroom, and actually lives in the hospital basement, as discerned by George in "The Name of The Game."
Yet she clearly adores Dr. O'Malley, which dawned on Izzie eventually, as the blonde beauty famously noted, "Oh my god... George is her McDreamy!"
In the episode "17 Seconds," Callie proclaims her love for George, later revealing that this was the first time she said that to a man. While he didn't say it back, he admitted that he wanted to give himself the chance to. Callie replied that she "hates that she's so into" George.
But she is, just the same. Despite breaking up with O'Malley early in Season Three and having a brief fling with Mark Sloan, she realized she wants to be with George and married him in Las Vegas - possibly in haste after his father had just died. She is not aware he soon had a drunken affair with Izzie, although Callie sure has her suspicions and is determined to keep her man.