First you have to conquer Shinnok and his alter ego. You can do this by using your Polar Blast. The Polar Blast can be charged with the Urn -- make sure you have at least four Urns (It takes at least five hits to kill him, so aim carefully). Remember, try not to use any Urns while going through the Earth Level. After the Credits, you should then be able to watch the Bloopers.