Dr. George O'Malley, played by T.R. Knight also called "Puppy", "007" (liscensed to kill), "Bambi"and "Curious George" by the other the other interns, is one of Meredith's roommates. He sometimes gets into arguments with others despite his positive and much more female personality.

Since he first met Meredith he had an infatuation with her. One day, when Meredith was totally depressed and sad, George tried to console her, ending up with a one- night stand. As Meredith started to cry during their encounter, George was very disgruntled and hurt in his feelings. This was the breaking-point of their friendship.