Character: Professor E. gadd (Super Mario Bros.)
My Choice: Hal Smith
Why Him? Gyro has what I think is a good elderly voice.
My Choice: Paul Frees
Why Him? I was inspired by this video to find a similar VA, wether dead or alive. In the end I decided that if Paul just changed Ludwig von Drake's voice to an english accent, or did an elderly Thomson and Thompson, I would likely be closest.
My Choice: Cliff Edwards
Why Him? Just hear Jiminy Cricket and you should not need more of an answer IMO.