Here's a cartoon, "The Stupidstitious Cat," that has perhaps the worst Jack Benny impression you will ever hear. It's the first "Buzzy the Crow" cartoon and is a one-shot for the Benny-esque cat.
Buzzy's voice clearly is meant to evoke Rochester: "My, oh my!" "Hold on, Boss!" and the like. The Benny-esque cat speaks in rhyme, but has some of Benny's verbal tics: "Well! I guess I get my wish!" "Yipes!" and so on. But it just...misses. So very, very badly.
The voice artist for Buzzy is Jackson Beck, who was doing Bluto in the Popeye cartoons about the same era. I don't know who did the cat, but it's a blessing he only did him once.