It's one of the few non-girlfriend related instances where the former US president JFK still gets ribbed -- his speech in Berlin on June 26, 1963.
It's said that in his speech he claimed to be a jelly doughnut.
While I'm pretty sure we all know that he wasn't actually a jelly doughnut, did he actually make such a gaffe?
Long story short, no. No he did not.
If you'd like the longer version, read on.
What President Kennedy actually said was,
"Two thousand years ago the proudest boast was civis Romanus sum ("I am a Roman citizen"). Today, in the world of freedom, the proudest boast is Ich bin ein Berliner! ...
All free men, wherever they may live, are citizens of Berlin, and, therefore, as a free man, I take pride in the words "Ich bin ein Berliner!"
The claim is that by putting the "ein" before "Berliner," he changed the meaning from "I am from Berlin" to "I am a Berliner." The claim then goes on to explain that a Berliner is a type of doughnut filled with fruit jelly. [*]
This is grammatically incorrect.
Before everyone who took a couple of years of German in high school begins waving their torches and pitchforks, yes, an actual native of Berlin would say, Ich bin Berliner. But JFK wasn't an actual native of Berlin, and to claim otherwise would be ludicrous.
So a indefinite article is needed to clarify that the statement is metaphorical. That's where the ein comes in. By adding it before Berliner, he's clarifying that he's not literally someone from Berlin. [**] So a better way to translate it isn't "I am a jelly doughnut," nor is it "I am from Berlin" -- but instead, "I am one with the people of Berlin."
Oh, and in certain areas of Germany a fruit paste filled doughnut is called a Berliner, but in Berlin itself those pastries are called Pfannkuchen.
David Emery of About.com has the best comparison to a similar thing in English, "...if I were to tell a group of Americans that my editor is a New Yorker, would any of them really think I'd confused him with the weekly magazine of the same name?"