There is no Voice Characterization listed in the credits because Mel Blanc does not actually voice any characters in this cartoon and the three actors who did provide voices did not have this listed in their contract.
Pa Bear's bed has "Oh You Kid" written on the side of his bed. It was a popular catchphrase at the time and was popularized by Groucho Marx.
Junior, like many characters of the time, was likely modeled after the slow witted Lenny from Of Mice and Men (1939).
Pa wears a red fez style Shriner's cap as he attempts to read. The Shriners, and many other fraternal organizations, were very popular in the postwar era.