Stefon made his triumphant return to "Saturday Night Live" ... and he made a big announcement at the end of his sketch. Bill Hader hosted the show last night for the first time since leaving SNL last year and his former costar Kristen Wiig made an appearance during the opening monologue and later…

Jan Hooks, who worked alongside some of the biggest "Saturday Night Live" stars ... died Thursday ... TMZ has learned. She was 57. We've learned she passed away this morning in New York City. Sources tell us Jan had been battling a serious illness. Jan was part of the 'SNL' cast from 1986-91 ...…