(If you have no idea what I'm babbling about, please consult the Invader Zim
The Irken races attempt at giving universal conquest a second shot. The Irkens are a race of short, green-skinned creatures with an insatiable, but hitherto unexplained, lust for conquest, commanded by the two with the highest status (ie. height), The Almighty Tallest.
Operation Impending Doom 1 failed when a staggering percentage of the Irken Armada was destroyed by a particularly bloodthirsty (but not altogether bright) Invader by the name of Zim.
Zim was sent to exile for his crimes to Foodcourtia, but unexpectedly showed up at the Great Assigning of Operation Impending Doom 2 and demanded to be assigned a planet. The Almighty Tallest, seizing an opportunity to get rid of him for good, sent him to a pair of random coordinates far, far away. Unfortunately for them, by an amazing stroke of chance, they nailed the precise coordinates for our planet, Earth. So while they're not completely rid of Zim, per se, at least he's not around to fuck up the current invasion.
So far, Operation Impending Doom 2 has yielded exactly one result: the successful conquering of the planet of the slobbering rat people.