I’ve noticed something of a trend at the Winter Garden Theatre over the past few years. Three of the last four productions that have played there have been musicals based on movies with iconic central characters. The one production that did not was about icons, but of a very different sort. The historical figures depicted in “Wolf Hall” are iconic, but not from movies, not from being embodied by a singular actor. Rocky, from “Rocky,” Dewey, from “School of Rock,” and Beetlejuice, from “Beetlejuice,” are very closely tied to the actors who played them originally, actors who were a big part of why the movies were so popular that they were adapted into musicals. As each one of these musicals has come to Broadway, most recently “Beetlejuice,” taking up residence in the Winter Garden this spring, I’ve had the same apprehension: the material may be good for the musical theatre treatment, but who’s going to get stuck toeing the fine line between doing his own thing and imitating an icon?