Celebs You Totally Forgot Guest-Starred on 'Grey's Anatomy'

Jeffrey Dean Morgan

Seasons: 2, 3, 5
The Walking Dead actor played the beloved Denny Duquette, a patient who needs a heart transplant. He and Izzie become an item, and she cuts his LVAD wire in order for him to get one. He later dies from a stroke. He also appears during Meredith Grey’s near-death experience and during Izzie’s hallucinations.

Hilarie Burton

Season: 9
The One Tree Hill actress played a plastic surgeon working on a pediatric case. She and Arizona Robbins had a one-night stand.