Until I saw this video, it was hard for me to believe that a single artist could voice so many characters effectively.  Dan Castellaneta and Harry Shearer show us their UNBELIEVABLE talent on Conan O’Brien's show. Dan reveals Homer, Krusty the clown, Grandpa Simpsons, Mayor Quimby and Groundskeeper Willie. Harry reveals Mr. Burns, Smithers, Principal Skinner, Dr. Julius Hibert and Kent Brockman. This is a MUST WATCH. Their talent is unparalleled.