A Grey's Anatomy season 1 reunion is happening with several original cast members. The show, which first aired in 2005, has had a successful run for 19 seasons. The reunion will include Ellen Pompeo, Justin Chambers, James Pickens Jr., Chandra Wilson, and Katherine Heigl, who controversially left the show in season 6. Wilson and Pickens Jr. will continue as main cast members for season 20. The reunion highlights the impact of the original core cast on the show's success. Grey's Anatomy season 20 premieres on March 14.