《曾有两次：《神秘博士》2017圣诞特别篇》是由彼得·卡帕尔迪,大卫·布拉德利,马克·加蒂斯,珀尔·麦基,莉莉·崔佛斯,杰瑞德·主演的一部科幻片，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.