It is perfectly legal to reference trademarked brands, titles, etc. in anything so long as you use common sense. If you make it unclear as to the origin or ownership of something, there could be cause for the actual trademark owner to take action (i.e. don't make it sound like you own or have anything to do with Final Fantasy, even vaguely). Anything tarnishing or slanderous would also be reason for them to take action against you, which is why often in advertising businesses refrain from mentioning competitors' products specifically and only generally, but there are ways to work around that.
In theory one could also take action if someone is using a brand name in some sort of commercial product as a generic use for a term ("xeroxing" as photocopying, "Band-Aid" for bandage, etc.), which is called trademark dilution. That obviously doesn't apply here.
And then there's the pure fact that, as Roph mentioned, Square Enix will never notice nor care, even if it weren't strictly legal (which it is). For what it's worth, and I'm not sure on this, you aren't supposed to put (TM) after Final Fantasy because you aren't the trademark owner and you didn't acquire the right to its use. Plus you aren't using the Final Fantasy logo. Plus putting (TM) is about as valid as using (c) for copyright; as in not at all.
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