It goes without saying that, in order to create the universe, God must be all-powerful, all-knowing, and basically absolute in every other way we can come up with. I say "it goes without saying" empirically, since over the course of my entire life, I've never seen anybody question it. Well, let's do something novel today. :)
The concept of simulated reality is an interesting one, and was on my mind because of the recent xkcd. A quick rundown for the non-CS majors (and ex-CS majors who never made it to Automata Theory :) in the audience: A cellular automaton (which is what the dude is doing with the rocks) has been proven to be equivalent to a Turing machine, and therefore is capable of any computation that any other Turing-complete machine is capable of. All computers are Turing-complete (well, unless you want to be a jerk about it and say that they're just finite-state machines), meaning that a guy in the desert with infinite rocks can run any program that any computer in the world can.
Now, if you accept even the weakest possible form of the simulation hypothesis - that, were we living in a simulated universe, it would pretty much look like this one - then you have to at least admit the possibility that God is, in fact, standing in a desert pushing rocks around. If we can assume perfect simulation, then there's no way for us to "peek under the covers". Or, to put it another way, if the universe is just a simulation, weoll never find out. An uninterested God is kind of depressing, but empirically, at least, it's indistinguishable from the alternative.
Let's go one step further. What if, a billion or two years ago, our God-of-rocks got bored of pushing the rocks around? After sitting around for a while, he decides to build a machine of some sort to push rocks around for him, because he's not a slacker like me and doesn't just drop projects halfway through. Now, there's no longer anybody at the helm; our universe is running completely on autopilot. Here's the neat bit, though: not only would we not notice the switchover, we wouldn't even be able to tell that a switchover had taken place. Our little machina ex deus has taken the reins without (from our perspective) skipping a beat.
Let's go one step further. Suppose that, instead of placing rocks in rows, our God-of-rocks had laid out a careful pattern of rocks at the top of an infinite hill, and then set them rolling in such a way that, as they bounced off each other, they fulfilled the rules of the cellular automaton. Now, he doesn't even have to build a machine; gravity will keep the universe running in perpetuity. There are a few key questions, though. The first, and easiest: what if the hill isn't actually infinite? What happens to us when the simulation, forgive the pun, crashes? The second: What if there was no God-of-rocks in the first place, and the rocks had just happened to be in a convenient pattern when they fell? Do we still get to exist? The third, and most brainbreaking question: There are some rocks on the other side of the hill, that fall at random. Do they end up creating a universe too? What about falling motes of dust, or flowing water molecules? Hell, since we're talking about cellular automata, what about our own cells? Could we, by our very existence, be creating simulated worlds?
Let's stop there. It's really easy to drive yourself crazy by following that line of reasoning too far.
...well, okay, one more. What makes a "real" universe any more real than a simulated one?