“You’ve got a lot of fans out there, people are posting, marching in the streets,” the prison security guard tells a young inmate with thick eyebrows, handing him a stack of fan mail. “Apparently, there’s even a musical.” “What kind of sick fucks would buy tickets to something like that?” the prisoner asks, prompting a round of laughter from the audience. It’s Monday night and Luigi: The Musical has made its New York City debut as a staged reading to a sold-out crowd at the Green Room 42, a