Doctor Who: 10 Times The Earth Was Invaded

2013's The Day of the Doctor saw the shapeshifting Zygons signing a treaty to seek refuge on the Earth, but in 2015 they had a change of plan. In The Zygon Inversion/The Zygon Invasion, a rebel faction of the creatures who had already infiltrated the planet decided that no longer should they remain hidden. Wanting to shed their assumed human forms and rise up against Earth's natives, the Zygons began a massive invasion across the planet.

Capturing and replacing humans all over London (including Clara Oswald), and even trying to assimilate Kate Stewart, the Zygons appeared to be succeeding in their conquest. With the help of one of the Osgoods, one of whom was secretly a Zygon, the Twelfth Doctor brokered another peace treaty between the co-habiting races.

Challenging them to compete in a scaled-down version of war in the form of the Osgood box - a kill-switch which would revert all Zygons to their true form or kill them - the Doctor convinced the warring species to stand down. Returning the real Clara to the Doctor, the Zygons realised that they couldn't win a war with the humans and negotiated for peace. With all parties on the same page, the invasion was called off.