Once upon an eternity ago, Mateus, who is a ninja, was at war with The Zombies. (They were much like the ones we know today, expect way deadlier.) Anyway, while engaged in combat, Mateus fell into an endless abyss that he designed for disposal of The Zombies. That abyss, which is impossible to escape, is now called the universe. From there he went on to create Earth, humanity, and everything else for unknown reasons. That is how he became God.
Mateus: "Ouch! Fuck, it's dark. Where am I? Oh shit, is this...? Damn it. Dang this is big - I wonder if there are still Zombies down here...this is gonna look bad on my autobiography 'The Story of Mateus'. (3 minutes later) I could really go for some sex right about now. I got it! Planet + animals + water = people! People = hookers! Hookers = sex! Oh, this is gonna be fun..."