This is a photo that I've seen making the rounds, which is supposed to parody the Ontological Argument (which is just the Argument from Being). This meme conceives of Eric the God-Eating Magic Penguin, and apparently since he is "God-eating" by definition, he has no choice but to eat God. Cute.
The person who formulated this argument has missed several key points of the Ontological Argument. When Anselm formulated the Ontological Argument, he argued that God is, by definition, a being greater than which none can be conceived. Why? Because if a greater being could be conceived, that being would be God. God just is, by definition, the greatest conceivable being.
So why can the Christian get away with this definition but the "God-Eating Magic Penguin" Eric can't? Because in God's case, it is a logical definition. What do we mean that God is the greatest conceivable being by definition? It doesn't mean that we're trying to arbitrarily define God into existence (as atheists who constantly misunderstand this argument allege). Think of a square. A square, by definition, has four equal sides and four corners. Now does that mean that we're trying to arbitrarily define a square as having four equal sides and four corners in order to distinguish them from triangles? Of course not. It just is the case that all squares have four equal sides and four corners. That is the concept of squarity. That just is what it means to be square.
So God, by definition, is the greatest conceivable being. That just is what it means to be God, because if there was a being that was greater, that being would be God.
So what do we make of this claim that it logically follows that God doesn't exist whether or not Eric does? Pure hogwash. First, God must exist. He is a necessary being. Every one of us, and all things in the universe, are contingent. This means that we do not have to exist, and cosmology has shown that the universe had a beginning (and that the universe is winding down and will eventually result in a heat death). Since everything in the universe is contingent, there must be a necessary being that is not contingent to have created the first contingent thing, otherwise we would be left with an infinite regress of causes which is a logical impossibility.
Second, the argument against Eric is not the same against God, as I have demonstrated. God is a necessary being (as part of his maximal greatness), and Eric is not. There is nothing in the nature of Eric which shows that he *must* exist, if he does.
Third, God could not possibly cease to exist, since he is a necessary being. This means nothing could eat God, so a "magic God-eating penguin" could not possibly exist because it is a contradiction in terms. This provides a positive argument against Eric.