Like many here, I've been listening to the Jack Benny Show in chronological order on MP3. This really allows a listener to get the full enjoyment of the program because most of the shows had running storylines and gags that carried on for several episodes or even longer. It also makes it possible to see the changes and growth of the program.
As those who have listened to the early broadcasts know, Jack's persona of the insecure, miserly coward did not begin until a couple of years had passed. At the beginning, Jack was the light-hearted, quick talking host with a slew of one-liners and creeky jokes (remember the awkward jokes about Gandhi wearing a sheet or "Scoop" Benny's Hollywood reports).
The Benny persona and the show's greatness really didn't begin until 1936 or 37 with the introduction of Phil Harris and the change in Mary's role from a scatterbrained man-chaser to the sarcastic foil of Jack's pretensions (a more natural fit for Mary's terrific timing). For the first year or so, Phil's role wasn't well developed, as the writers didn't seem quite sure how to best use him. But as they changed him from his initial character of a dour slow-witted tough guy to the fun-loving, jive-talking hipster, they finally took full advantage of Phil's brilliance as a comic actor. The changes in Phil's and Mary's roles allowed the writers to fully develop all of the elements of Jack's personality that came to shape the program. With the addition of the fantastic Eddie Anderson, the final element was in place for the sustained greatness of the Benny program.
If Jack's show had stayed where it was in 1935, none of us would be talking here about Jack or his show. The period from 1936 to 1939 representing some of the most brilliant and inspired comedy writing in the history of radio. During those three years, Jack's program went from being good but unmemorable to truly great and transcendent.