10 MORE Doctor Who Episodes You Didn't Know Were Connected
9. The Dalek Invasion Of Earth & The Stolen Earth
Many connections between Doctor Who episodes are extremely subtle. And other times, the Doctor just says them out loud.
Series 4's The Stolen Earth features - if you can believe it - someone stealing the Earth. This is the work of the Daleks, who are using our planet as one of the 27 worlds needed to power their reality bomb.
When the Doctor realises what's going on, he says "Someone tried to move the Earth once before". It's a bit of a throwaway line, so it's very easy to miss what the Doctor is actually referencing here.
In 1964's The Dalek Invasion of Earth, the Daleks... invade the Earth. Part of their plan is to replace the planet's core with a device that will allow them to pilot it around the universe. Thankfully, the First Doctor and his friends were on hand to stop the Daleks from turning Earth into an intergalactic minibus.
Ten regenerations later, the Doctor used his knowledge of this encounter to deduce that his greatest enemies were up to their old planet-moving ways once again.