Doctor Who: 10 Clever Moments Of Foreshadowing You Probably Missed

Series 4 was stuffed to the gills with ongoing story arcs, each of which were signposted multiple times throughout the 13-episode run: the return of Rose, Donna's Time Beetle, the disappearing bees, and of course, the missing planets.

As revealed in the finale, the missing planets were caused by the Daleks, who had taken them out of time and space and moved them to the Medusa Cascade. This was done in order to power their reality bomb, which, if detonated, would destroy planets, solar systems, and galaxies: every ounce of matter in the multiverse.

In other words, the stars in the sky would start to disappear, an ominous scenario that was sneakily foreshadowed in the previous year's Christmas special, Voyage Of The Damned, where an excited Astrid Peth - upon taking a quick trip down to the surface of the Earth - points in the air and proclaims "Look! No stars in the sky."

At first, it sounds like she's referring to a simple cloudy evening, but on reflection, this was clearly an early hint that the reality bomb could've already penetrated certain corners of the multiverse - as seen later on in Series 4's Turn Left, where the stars begin to vanish from the sky right before Wilf's and Donna's eyes.