Ellis was a world famous surgeon who shared a strained relationship with her daughter. The character developed Alzheimer's later in the series, and eventually died in season three. She last appeared in season eight during Meredith's alternate universe fantasies, and will appear in flashbacks in the new episode.
Burton has been nominated for an Emmy twice for her portrayal of Ellis, and is currently nominated for her role as vice president Sally Langston on Scandal. The actress has also appeared on Law & Order, The Good Wife and Veep. Both Grey's Anatomy and Scandal were created by Shonda Rhimes.
Grey's Anatomy season 11 premieres September 25 on ABC.