There is very little left to be said about Nyan Cat, except that it's my profound disappointment to inform you that Konami did not, in fact, release a licensed Nyan game in 1988. Not only would Nyan Cat vs. Tac Nayn have made a fantastic little game (a shmup, perhaps?), but it would have given this box art -- a mock-up by artist J. R. Baker -- an excuse to exist.
The funny thing about Baker's project -- beside the idea's pop cultural capital -- is that it wouldn't have exactly been out of place next to games like Mega Man or Phalanx. The box art for those games could only have been borne out of the collective, cocaine-fueled fever dream of the late '80s, so Nyan Cat's in good company.
I also particularly like the KB Toys sticker Baker included -- it's a nice touch.
If you're disappointed that Nyan Cat vs.Tac Nayn isn't a real game, don't be. Channel that impotent fury into buying a print of the illustration. Baker suggests an opposing diptych, so that the two adversaries can be forever locked in combat on your wall.