No subject matter can be said to be the exclusive purview of its own academic domain. Politics for instance have draw heavily from Philosophy (at times), and likewise contributed to it. Presently I am reminded how much Literature speaks on Philosophy in an 'informal' way.
Many times has it happened that I reread a book, last read as a child, only to find philosophical opinions, I held as my own, reflected therein. Notably Terry Pratchett and Douglas Adams, who both have not only satirically presented a slew of philosophic topics, but also reached a wider audience than Kant ever will. An example apart from fictitious works would be Douglas Hofstadter who discusses more particular problems informally.
That said, and specifically for works of fiction, it should be noted that it may be challenging to reference such work. Arguments are frequently not stated explicitly, and rarely carry any support but for an accompanying thought experiment. Technical terminology are eschewed and thus mostly open for interpretation...
Can "armchair" philosophy be discussed on this site, given that it originates from a (well known) work of fiction?
EDIT: This question has been flagged as duplicate to the linked question. I note that question didn't cover the specific focus of this question, I'll leave it here provisionally for this reason: Real philosophy presented (seemingly) accidental/incidentally in a professed work of fiction.
Note however, I would 'accept' @Cerberus answer to the linked question here.