Anyone who’s ever been to basic training knows that the relationship between trainers and trainees is strictly lopsided: The drill instructor screams orders, and the new recruits follow them. There’s no small talk. No in-between. So when Sgt. 1st Class Vincent Vargas, a drill instructor in the U.S. Army Reserve, recently found himself being addressed as “Rocco,” his nickname, by one of the privates in his charge, he was, understandably, caught off guard.