SEASON PREMIERE: Season 1 of Stranger Things sort of sneaked up on everyone, becoming a pop-culture cult hit on the basis of its Eighties nostalgia and its classic horror-story sensibilities. Season 2, at least in the four episodes on which I’ve binged this morning, holds up the tradition and the energy, introducing some new characters (played by Sean Astin and Paul Reiser, whose resumes are hints to one reason they were cast) and introducing new mysteries that are part jigsaw puzzles, part Gremlins allusions, and a lot more visits to and from Down Under. The action begins in 1984, circa Halloween, with a presidential election around the corner, and with the gang dressed up as – what else – Ghostbusters!