If you got the limited edition demo of Modnation Racers then lucky you! I got it too! If you missed, however, do not fret! Just use an American account to go onto the US playstation store and buy the demo.
On another note this demo is more useful as you think! You can create your own tracks, demo mods and demo karts and transfer them to the full version.
And on yet again another note theres already buzz about Modnation Racers DLC! Be sure to be watching PSN!
And last but not least the full version has 10x more creative bits and bobs than the demo! So get it!
If you pre-order it in game you'll be garanteed a Sackboy Racer Code!