If you've played through Stubbs at least once already, all the way to the end, at any difficulty level, you will have unlocked the audio developer commentaries strewn throughout the game. You can trigger them by walking over one of the many pink hippo heads you'll see, as pictured here.

The loading screen for the first level of Stubbs the Zombie, Welcome to Punchbowl. As with all of Stubbs' loading screens, the animation that plays slowly turns the screen green while ever-loudening groans of "brains... brains" by a zombie horde plays wistfully in the background.