In 2008 the episode Turn Left showed the horrifying aftermath of a simple change of heart. While driving to a job interview, Donna Noble (Catherine Tate) is manipulated into taking a right turn, instead of the left she took in the previous version of history. As a result she never gets to meet the Doctor, who subsequently dies. Without the Doctor’s intervention the Earth descends into a chaotic dystopia and millions fall victim to alien invaders.
The consequences of a timeline without Doctor Who – the television series, that is – might not be quite as dramatic, but it’s fun to ponder some of the programme’s own forks in the road.