Curiosity must have hit some people when they saw Arcade Fire perform for “Saturday Night Live” on Sept. 28. It was the first televised performance of Arcade Fire since they concluded the tour of their 2010 Grammy-winning tour de force “The Suburbs” and since they began a curious ad campaign behind their upcoming album. Something seemed very off: these were the faces of Arcade Fire, but no one could recall them in such a strange style.