Kate Walsh Goes Public About Private Practice As Addison Montgomery, Kate Walsh has gotten to play one of the smartest, sassiest women on TV. Addison entered Grey's Anatomy at the end of the first season and quickly became a favorite — so much so that she scored her own spinoff, Private Practice, last year. Earlier this week, I got a chance to chat with Walsh about some of the changes to Private Practice this year and her all-time favorite Addison moments.