ANSWER
The voice of Horton, and of Dr. Hoovey, was Chuck Jones.
Chuck Jones was an animator, writer, director, and producer who worked on over 300 animated films in a career spanning more than 60 years. It was his work that defined the personalities of Bugs Bunny, Daffy Duck, Elmer Fudd, and other ubiquitous Warner Brothers characters. His was the mind responsible for creating the Road Runner and Wile E. Coyote, Pepe Le Pew, Marvin the Martian, Sam Sheepdog and Ralph Wolf, and Michigan J. Frog. Jones won three Oscars for his work, in addition to a lifetime achievement award.
Chuck Jones passed away February 22nd, 2002. He was 89.
