There’s the Indy 500, and then there’s the NC-500. “NCIS” will air its 500th episode Tuesday night — a rarefied air shared in scripted prime-time television only by “Gunsmoke,” “Lassie,” a couple of “Law and Order” series and a couple of animated shows, not all of which were actually on the air for as many seasons as the 23 “NCIS” has racked up. The show plans to offer up a surprising development ...