Creator Shonda Rhimes revealed that Ellen Pompeo and Sandra Oh will star in a special two-hander episode in the upcoming ninth season.
"It's just the story of Meredith and Cristina," Rhimes told TVLine.
"It's really going to be original. I don't think we've ever told a story the way we're telling a story in this episode."
Rhimes added that she couldn't explain the style of episode in question, but insisted that it will be "different".
"It's not a regular episode," she teased. "I won't be able to explain what the gimmick is until I've seen it shot and we've decided on the visual style of it. But it is going to be fairly different."
Shonda Rhimes recently hinted that the medical drama may feature further cast exits in its ninth season.
Grey's Anatomy's ninth season will premiere on Thursday, September 27 on ABC.