The caricatured celebrities are, in order of appearance: The Crooner: Frank Sinatra; "Shortenin' Bread": Nelson Eddy; "September in the Rain": Al Jolson; "Lullaby of Broadway": Jimmy Durante; "Blues in the Night": Cab Calloway; The Old Groaner: Bing Crosby.
The only Porky Pig cartoon to be nominated for an Academy Award.
Flockheed Farms is a pun on Lockheed Aircraft, which was busily producing planes for the war effort at the time.
Frank Sinatra was probably voiced by a member of The King's Men, a group that had performed for other Warner Brothers shorts.
WW2 era sight gags, such as ID badges and other things unique to the era would have been recognizable to audiences of the time but might not be known today. This includes the crooning stars, fainting fan girls, saddle shoes, bobby socks, and the boxes of eggs destined for Britain, China, and Russia (allies at the time of the USA).