It’s a drag to feel you’re being held hostage by someone else’s nostalgia. The stage show Wicked is beloved by many; it’s been playing on Broadway for 20 years and counting, which means a lot of little girls, and others, have happily fallen under the poppy-induced spell of Winnie Holzman and Stephen Schwartz’s musical about the complex origins of the not-really-so-bad Wicked Witch of the West.