When a 1991 TV Guide listed "Nazis on Tap" as a short following a repeat showing of The Simpsons' classic 'Bart the Daredevil,' no one was more surprised than the show's creators. 'Nazis on Tap' was never animated and, according to some sources, was never even intended to be seen. But there was a script, and that script was recorded by the show's voice actors, and there were even character designs created for the short. So what happened?
The short answer: as of today nobody quite knows. There's speculation that the short was created mostly on a dare, an attempt to find some comedy in Hitler (which had been done long before The Simpsons, of course). 'Nazis on Tap' was actually set in the 40s, and featured 40s-style versions of Bart and Homer. In the short Homer hits the local bar after a hard day working at a defense factory, and he's served by an anthropomorphic dog, likely a joke about the species mixing of WWII-era propaganda cartoons. While complaining about his job, Homer accidentally spills some national secrets to Hitler, who is hanging out at the bar. Hitler gets routed and FDR shows up to tie a ribbon on the short, bringing along Joseph Stalin, who is still America's pal.
It's not great. It almost sounds like something that was thrown together to pass some time; there's a germ of an idea in pretending that The Simpsons were making animated shorts in the 40s, but it all feels more Family Guy than classic era Simpsons. Some sources say that the audio was thrown together just as in-joke for the animators, which accounts for how short and semi-lame the whole thing is. The concept was put to much better use in the episode 'Itchy & Scratchy: The Movie,' where Hitler gets his head cut off and FDR kicks Itchy and Scratchy in the asses.