Here's an old Kool-Aid commercial from the sixties with Mel Blanc as Bugs Bunny and Hal Smith as Elmer Fudd. You may remember Hal as Otis the Town Drunk on The Andy Griffith Show. He also had a great career doing voices for cartoons, though apart from fill-ins as Elmer (and once in a rare while as Mickey Mouse or Goofy), he never did a character that most of you could recognize. He was a very funny, nice man and a real good actor…
Arthur Q. Bryan, who was the original Fudd, died in 1959. You can see a clip of Mr. Bryan over here. Even before he passed on, they occasionally had to have someone fill in for him in the role. Mel did it now and then for a few brief lines. Dave Barry seems to have been the guy who did it in a few kids' records and in the Bugs Bunny short, Pre-Hysterical Hare.
The great storyman Michael Maltese once told me that after Bryan's death, someone at the studio suggested that since the voice was so hard to mimic, the character should just be abandoned. Maltese then did an impression of some studio exec reacting in outrage, screaming it was a bad precedent: "Then are we expected to abandon all the rest when Mel dies?" They not only didn't drop Elmer, they seem to have increased his appearances. Hal Smith did most of them but eventually, Mel took it over.
Since Mel died, a number of different people have attempted to speak for Mr. Fudd. The best in my opinion has been Billy West. You heard him in this Geico commercial…