For some, a defacement page from the PBS LulzSec hack will be the first introduction to Nyan Cat. For others, the animated pop-tart rainbow feline is already a familiar form of internet meme happies, despite having originated just two months ago.
This Know Your Meme feature is a good place overview of its origins. The attention-deficit-version is this: PRguitarman created it. Everything began on April 2, 2011, at LOL-COMICS, then hit Tumblr, and from there, mutated and spread rapidly like so many strains of gleeful, 8-bit ebola.
Below, one of the early videos to surface; and following that, a dubstep remix of the same, both via Laughing Squid.