Guest Who: Nash Icon's Reba McEntire will serve as a guest judge on this season of NBC-TV's America’s Got Talent. She will join regulars Simon Cowell, Heidi Klum, Mel B and Howie Mandel. Other guest judges include Ne-Yo, Louis Tomlinson and George Lopez. The show airs Tuesdays at 8/7c; guest judges will be featured after July 12.