10 Doctor Who Episodes That Accidentally Changed The Show Forever

Reality under threat from Davros and the Daleks, the return of Rose, and David Tennant's Tenth Doctor regenerating, all with one episode still to go! It's not without reason that a lot of fans consider The Stolen Earth the most epic cliffhanger in the show's history. But it's also one of the most important too.

In Journey's End's opening moments, Russell T Davies resolves this unresolvable cliffhanger quite ingeniously – by having the Doctor blast his excess regeneration energy into a handily-placed hand, allowing himself to heal without changing his face. In the process he accidentally creates the Metacrisis Doctor, a human clone of his tenth incarnation.

So all's well that ends well! Rose gets a human Doctor to stay with on her alternate Earth, and the real Doctor gets to keep David Tennant's fan-favourite face. Job's a good 'un.

Except for one little quibble.

Five years later when Steven Moffat sat down to write Matt Smith's final episode, he realised something: if the Doctor's regeneration in The Stolen Earth counted (and after he'd sneakily inserted the War Doctor between Eight and Nine for The Day of the Doctor) Matt Smith was actually the Thirteenth Doctor. He had no more regenerations left.

In response, Moffat wrote The Time of the Doctor, where his 'crack in the wall' story arc culminated with the Doctor gaining a brand-new set of lives from the Time Lords.

If RTD had picked literally any other solution to his big Stolen Earth cliffhanger, Moffat's tenure as showrunner could've taken a very different course.