The title refers to the Pied Piper of Hamelin, a legend about the abduction of many children from the town of Hamelin, Germany and used in stories written by the Brothers Grimm and Robert Browning.
Although WW2 for the US was still two years away, there are some references to American military prowess (at the time) here.
The big band era of music was popular at the time, as nodded to by Porky playing his instrument 'licorice stick' style, a la Benny Goodman, the King of Swing.
The humor in this short is more adult in nature, as cartoons were shown in a cinema to a variety of audiences. There are inside jokes that the grown ups would have appreciated, plus plenty of slapstick to amuse the kids.