Mel Blanc was rejected by Warner Brothers every two weeks for two years!

Mel Blanc, the voice of nearly all Warner Brothers' cartoons, went to Warner Brothers every two weeks for TWO YEARS asking for an audition. They always told him "Thanks, we already have all the voices we need." Fortunately, he was determined and finally bonded with another musician at the studio who listened to his voices and then got him an audition.

http://www.youtube.com/watch?v=nPUUZ2XETI8