Isabella Pappas as Joyce Maldonado, from left, Oscar Lloyd as James Hopper Jr. and Christopher Buckley as Bob Newby in the rehearsal room of “Stranger Things: The First Shadow.” Next month, the Upside Down extends its tentacles into London’s West End with “Stranger Things: The First Shadow,” a prequel stage production that expands the world of Netflix’s sci-fi/horror blockbuster. Kate …
