Nyan Cat is a looping video depicting a cartoon cat with a poptart
attached to his back and flying through space while
singing a repetitive "NYAN NYAN NYAN" sound and leaving a rainbow trail.
The video became a viral internet meme in YouTube.
The origin of such meme it's believed to be in the "Buttered Cat Paradox" which states that
a buttered bread will
buttered side down
and a cat will
on their feet, so attaching
a buttered bread (or a poptart
) on a cat's back will cause
effect making the cat to float indefinitly. (This doesn't explain the NYAN NYAN sound, but I believe that
was added to the video just to make it cute... and annoying)