Mel Blanc did nearly all the voices.
Since everyone else has already quoted all my favorite moments, I will hijack, momentarily, to recite some history:
When the Warner Brothers animation studio created a wacky duck character, there was some confusion as to what kind of voice the duck should have. Mel Blanc needed some kind of direction. A celebrity impersonation? A Brooklyn accent? A Texas drawl? What to DO?
About then, producer Leon Schlesinger came in to bark some orders, shuffle some paperwork, and storm back out.
Schlesinger apparently had a thick, weird lisp, and someone else thought it would be funny to…
No one seems to remember whose idea it originally was, but somehow, Mel Blanc wound up doing a sort of Leon Schlesinger impression, and everyone thought it was hilarious… and voice work began on the first Daffy Duck cartoon.
The short was nearly finished before it occurred to someone that before the short was released to theatres… Leon himself would want to view it.
Panic reigned, but it was too late to go back and redo the voices. They’d either have to brass it out, or tell Schlesinger that they’d somehow lost the master copy… and either option was likely to get them all fired.
Sadly, the optimists prepared their letters of apology and the pessimists, their letters of resignation.
And the day arrived for the studio screening. They stuck the duck cartoon in a big stack of other features Schlesinger was due to review before releasing, hoping against hope he wouldn’t notice, or perhaps he’d leave before the projectionist got to it.
Fat chance. The duck cartoon was among those in the first half hour. The animators cringed and waited.
Schlesinger watched the short in stony silence. He did not laugh. He seldom did; he apparently didn’t have much of a sense of humor, even for cartoons that were not directly mocking him.
After the cartoon was shown, the lights came up. Everyone looked at Schlesinger with bated breath.
After a pause, Schlesinger said, “Well, that wath good. Print it. Gee, that duck had a funny voith. Where’d you guyth get that voith?”
(cite: Leonard Maltin)