Continuing a storyline introduced on sister show "Station 19," the longest-running American primetime medical drama series opens its 18th season with "Here Comes the Sun." After a season that saw several characters from the show's past resurface as visions in then-patient Meredith's (Ellen Pompeo) mind, two more return "for real" in these new episodes. Abigail Spencer is back in this premiere as Dr. Megan Hunt, while Kate Walsh will reappear at some point as Dr. Addison Montgomery. Kate Burton also returns in her role as Meredith's late mom, Dr. Ellis Grey.