premise: Kate Walsh portrayed the role of Dr. Addison Montgomery on Grey's Anatomy.
hypothesis: Dr. Addison Adrianne Forbes Montgomery ( formerly Shepherd ) is a fictional character on the ABC television series Grey 's Anatomy and Private Practice played by Kate Walsh . Kate Walsh (actress) . Her roles include Dr. Addison Montgomery on the ABC television dramas Grey 's Anatomy and Private Practice , Rebecca Wright on the short-lived NBC sitcom Bad Judge , and Olivia Baker on the Netflix drama series 13 Reasons Why .