The newsreel presenter "Cold Promise", appearing around the 3-minute mark, is a caricature of the famous member of that profession, Lowell Thomas.
A movie poster (seen around 1:50) advertises "Ahs of a Wizard" -- a word play on The Wizard of Oz, released in the same year, 1939, by a rival studio.
As the children gather in front of the theater, two of them (seen on opposite sides of the ticket booth) closely resemble Donald Duck and Mickey Mouse.
The Masked Marvel is actually the Lone Stranger from an earlier film, The Lone Stranger and Porky (1939) The animation was re-used for this film.