4) Twice Upon A Time
The most recent addition to this list is 2017’s Christmas special – perhaps the last Christmas special – “Twice Upon a Time.” The episode was a hugely significant one as it marked not only the end of the Twelfth Doctor’s era but also Moffat’s as showrunner. We’ve established by now that the writer’s a big fan of multi-Doctor stories, so naturally he decided to make his last episode a reunion between Peter Capaldi’s regeneration and one of his past selves. Specifically, the First Doctor – the original, you might say.
Harry Potter actor David Bradley stepped into William Hartnell’s shoes as Doctor Numero Uno and did a terrific job at matching Hartnell’s mannerisms while also bringing his own twinkle and charm to the part. His First Doctor makes a wonderful contrast with Twelve as well – despite looking older, he’s so much younger and is shocked at how much he changes as a person by the time he’s reached his twelfth life.
The story might be a slight one – as the Doctors encounter kindly glass people the Testimony and take a trip to the Christmas Armistice of World War I – but “Twice Upon a Time” is a touching love letter to Doctor Who‘s beginnings and a perfect farewell for a terrific era of the series.