The Rocky Horror Picture Show holds the distinct honor of being the longest-running theatrical release in film history, a phenomenon likely no one saw coming when it first debuted in 1975. Rocky‘s staying power can undoubtedly be attributed to audience participation and shadow casts—the groups of actors who perform the entire movie in front of the screen, complete with props, costumes, and rapid improvisation. Audience members also dance along to the Time Warp, throw objects around the theater (when allowed and...