Peter Capaldi’s final episode of Doctor Who this Christmas will feature Pearl Mackie as Bill Potts and be called Twice Upon a Time, it was revealed this evening (23 July) during a cast panel at San Diego Comic Con. Viewers will have to wait until Christmas to discover exactly how Bill, who will appear throughout the episode, makes her return. 　　《曾有两次：《神秘博士》2017圣诞特别篇》的上映日期是2017-12-25(英国)。 《曾有两次：《神秘博士》2017圣诞特别篇》的别名有：Twice Upon A Time。