The Year of the Slow Invasion

The Year of the Slow Invasion toke place in 2020 - 2021, roughly from July to the next July. It was masterminded by the Shakri, who sought (almost like every other alein species) to eliminate humanity. And like usual, the Doctor undid the harm.

History
Believing humanity to be a plague that would bring ruin to the universe should they go out into the stars to colonise, the Shakri decided to conduct "pest control" by sending their cubes to infilatrate Earth. They were inactive, but still were believed to be a threat; the Eleventh Doctor, Kate Stewart, and Brian Williams decide to watch the cubes until some kind of activity occured. The cubes were subjected to numerous tests by UNIT to see what could destroy them; though human methods, it was impossible. Eventually, the Shakri began using an android to command fake Orderlies, which kidnapped multiple humans from some unknown purpose, over the course of the year.

When an entire year had past, every last cube performed some random function; some of them were harmful (such as spewing fire and causing mood swings) or just plain annoying (like playing the "Chicken Dance"). The cubes then sucked in electricity, using it to stop the hearts of 1/3 of the human population. The Doctor, along with his in-laws, Amy and Rory Williams, infiltrarted the Shakri ship and used the cubes programming to restart the hearts they previously lost. The contridiction of the Shakri's methods caused one of their ships to explode, sealing them back outside the universe, for then. (TV: The Power of Three)