Before you check out Zack Snyder’s action-packed flick, learn how it came to be. By Kara Warner Emily Browning in “Sucker Punch” Photo: Warner Bros./ Legendary Pictures Way back in October 2008, amid the buzz surrounding Zack Snyder’s big-screen adaptation of “Watchmen,” news broke about plans for his next project, an original screenplay penned by Snyder and Steve Shibuya called “Sucker Punch,” billed simply as “Alice in Wonderland with machine guns.” For Snyder’s devoted fanbase, that descriptor was enough to set minds speculating and Internets buzzing for well over two years. Naturally, MTV News has been following the project from conception to opening day Friday (March 25). Here’s everything you need to know about “Sucker Punch”: First, in addition to the “Alice in Wonderland with machine guns” tease, the initial logline announced that the plot revolved around “a young girl institutionalized by her wicked stepfather. Retreating to an alternative reality as a coping strategy, she envisions a plan which will help her escape from the facility.” In March 2009, an all-female cast was announced, with several of Hollywood’s most in-demand ing