One of the pleasures of listening to the Jack Benny show has been connecting the voices of some of the characters to cartoon characters I grew up with. The obvious person here, of course, is Mel Blanc. But there are some others:
Andy Devine: not sure if he counts as an actual character on Jack's show, but he seemed to turn up fairly regularly in some early shows. He did the voice of Friar Tuck in Disney's "Robin Hood," and I think some other Disney voices as well.
Phil Harris: the other big cartoon voice -- Baloo the bear in "The Jungle Book," plus characters in "The Aristocats" and "Robin Hood."
Dennis Day's Mother: the Queen of Hearts in "Alice in Wonderland"
Dennis Day: Johnny Appleseed
Harry Shearer: multiple voices on "The Simpsons"
Can anyone think of any others?