A new generation of heroes has revitalized television. These daring, dauntless young actors have fans swooning and critics raving. Matt Smith (Doctor Who), Kit Harington (Game of Thrones), Steven Yeun (The Walking Dead), Tyler Posey (Teen Wolf), and David Giuntoli (Grimm) discuss the thrills and fears of taking on iconic characters, reveal how they broke into the business, and share their favorite stories from set.