Kate Walsh calls returning to 'Grey's Anatomy' as Dr. Addison Montgomery 'completely surreal'

Dr. Addison Montgomery will officially check back in to Grey Sloan Memorial Hospital on tonight's episode of Grey's Anatomy, and Kate Walsh is soaking up the unexpected opportunity to reprise the character.

"Completely surreal," Walsh told Entertainment Tonight of her anticipated Grey's return. "Like, there's no way to even articulate it. I knew it would be odd but it was so emotional, and so big and yeah, beyond, because when's the last time you've ever gone back to a job that you started 18 years ago that you left 10 years ago? You know what I'm saying? There's no infrastructure. There's no construct for it because even if you say, 'Oh, it's kind of like going home to your parents,' and you're like, 'Wait, this is my room? OK, yeah, that's right I have an airplane bed.'"

Walsh debuted as Addison in the record-breaking primetime medical drama's first season finale—surprising her then-estranged husband Dr. Derek Shepherd (Patrick Dempsey) and finding that he had fallen in love with intern Dr. Meredith Grey (Ellen Pompeo). 

Addison's arc as a series regular ended when she left to lead spin-off Private Practice, but the beloved OBGYN had spotty guest appearances until February 2012's "If/Then" episode.

It was announced in early September that Walsh was reprising the role for the 18th season of Grey's, which premiered Sept. 30: