Brilliant use of non-actors
Ben Sliney and the military officials bring a verisimilitude that you just can't get from a casting director, and in different ways. Sliney is the perfect embodiment of what we might imagine in his role; by contrast, the military officers ironically don't have the "military look" we generally see in movies, something to keep in mind when watching future films.
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See a list of my favourite films here: http://www.flickchart.com/slackerinc