By memory, this stirring ta-daah! intro was used in a few other shorts of that era. Always a surprise... if not that, then a tiny, blinking Spanky greeting the viewers, or, out of the blue, "For No Reason At All" replacing the regular theme in Pups Is Pups, as indeed another bouncy tune did at the beginning of "Mike Fright."
I get the sense that much if not all of this was somewhat random, which IMO makes it all the more enjoyable. But, FWIW, I did not like the switch to the later, more upbeat (major key!) version of "Good Old Days" in the later (Alfalfa-era) shorts.