10 Biggest Doctor Who Retcons
5. The War Doctor
Series 7's finale The Name of the Doctor ended on a shock cliffhanger that not only went on to form a crucial part of the 50th Anniversary special, but changed Doctor Who canon as we knew it forever. Having jumped into his time stream to rescue Clara, the Eleventh Doctor discovers a memory he had suppressed for centuries, kept secret out of fear and regret.
As it turns out, the Doctor underwent a secret regeneration between his eighth and ninth incarnations. This hidden incarnation is known as the War Doctor, played sublimely by the late John Hurt. The War Doctor is so called because he's the one who got his hands dirty in the Time War. But hang on, wasn't it very strongly implied that it was the Ninth Doctor who fought in the Time War? Isn't that where his rueful, anguished character comes from?
Not only does the addition of the War Doctor retroactively mess with the Ninth Doctor's character arc, it also messes up the numbering of the Doctor's incarnations. Next time someone asks you to count to 10, throw a cheeky "War" in there between the 8 and 9 and see how they react; that's how jarring it was back in the day. We thought Matt Smith was the Eleventh Doctor, but actually he's technically the Thirteenth (when you include the Metacrisis Doctor regeneration - which you should). This is one retcon so big it required fans to take a day off and recalibrate.