MutitlatorTroy says:" This is the audio track to an unaired Simpsons short entitled 'Nazis on Tap.' From what I understand, Matt Groening didn't want the writers to put Hitler jokes into the show. To spite Matt, Sam Simon had this put into production in secret. When Matt found out, the short was canned. Only the audio track and character designs were finished, and was planned to air after 'Bart the Daredevil.'"

The Simpsons Archive knows more: "It was called "Nazis on Tap", and started off with Harry Shearer doing an announcer's voice saying something like "And now, here's a short from the Simpsons archives, from the year 1944." Homer was in a 40's version of Moe's Tavern (for some reason, the bartender was a dog; perhaps someone else can supply a more specific reference for why they would have done this. I just have a vague feeling that this sort of species mixing was common in a certain style of cartoon), relaxing after a hard day's work in the defense plant. Hitler sits next to him at the bar, and starts pumping him for information about weapons and invasion plans -- Homer of course answers all the questions. Then Bart comes along, spots Hitler, and chases him. The final scene is of Roosevelt giving Bart a medal for capturing Hitler; when Bart starts to chase after another man who is present at the ceremony, FDR says "No, no, that's Joseph Stalin, our friend!" The short ends with Bart saying "Catching Hitler was neato! Next stop, Hirohito!"