The first time I saw The Rocky Horror Picture Show, my friend and I snuck into one of the long-running midnight screenings at a theater in Chelsea. The movie’s night-owl devotees were already riled up, shouting in unison at the screen and lobbing foreign objects in the dark. How were the ushers letting people get away with this?! We nabbed seats in the back and kept our newbie status to ourselves: Rocky Horror “virgins” are subject to public initiation rituals, the humiliation of which I imagine often involves scarlet lipstick and no small amount of innuendo.Since its premiere in 1975, The Rocky Horror Picture Show has enjoyed the longest theatrical run in history , with midnight screenings that continue in New York and around the country to this day.A loving, rock-’n’-roll sendup of B horror and sci-fi flicks, Rocky Horror opens on a couple of squares named Brad and Janet (Barry Bostwick and Susan Sarandon) who get a flat tire on a cold, rainy night. As they search for help, the pair stumbles upon the castle of Frank-N-Furter (Tim Curry), who bills himself as “a sweet transvestite from Transsexual, Transylvania.” A number of other colorful characters are packed inside — including Rocky, “a living muscular man,” the eye candy equivalent of Frankenstein’s monster. And who could forget Meat Loaf, riding out of a deep freeze on his motorcycle? Murder, adultery, cannibalism, and cabaret — among other otherworldly antics — ensue.Fox’s small-screen remake, The Rocky Horror Picture Show: Let’s Do the Time Warp Again, premieres October 20, starring Laverne Cox as Frank-N-Furter and featuring a supporting cast that includes Adam Lambert and Christina Milian. Given that the original has been drawing new generations to theaters for 40 years, it’s hard to imagine a more obsessive fan base. The TV movie has a lot to live up to — to say the least.Here are five things to know before diving into the campy, twisted world of Rocky Horror. Whether you still consider yourself a virgin by the end is, as virginity tends to be, a matter of personal choice.