The concept of "viral meme" is not a mainstream academic concept, and only merits the briefest mention in an encyclopedia.  "Meme" is already treading on thin ground, but is at least well known enough to be semi-respectable.  "Let's roll" isn't a concept at allit's a phrase that has made the news recently, and it's the title of a song, both of which deserve to be covered.  "Move zig" is another phrase, probably meaning more or less the same thing, but it isn't worthy of inclusion here.  It isn't even a common enough idiom to be found in a dictionaryyou certainly wouldn't find it, say, in a New York Times used without reference to its source.  LDC