I've been taught that when one mentions an object for the first time and it's countable, one should use a/an before it. I know that there are exceptions, when you speak of a renoun object which everybody knows, like the moon.
But I cannot see why the author uses definite articles in some places in this piece:
"It had better use THE advertisement with THE shirtless guy rather than THE shirtless girl."
That ad/guy/girl were mentioned in the text for the first time. Why does the author uses the definite article before them? And could you please provide some rule which would clarify the usage of articles for me?