Ich bin ein Berliner

The phrase "Ich bin ein Berliner" (German: "I am a Berliner") was used by President Kennedy during a speech on August 13th, 1961 in Berlin after the Berlin Wall was erected. The meaning was to establish that every free person is united together in purpose in Berlin.

Kennedy was given a proper and grammatically correct statement to say, however many English speaking people, only aware that German generally doesn't use the indefinite article before a profession, or place of origin, presumed that the statement must be wrong. No less, they later find that there was a donut, called "ein Berliner", and announced that Kennedy accidentally said "I am a jelly donut" instead of "I am a Berliner."

These people are entirely retarded, because the term "Berliner Pfannkuchen" was not widely used at all until after Kennedy's speech, because at the same time as the "Berliner" donut was becoming more well known, the Berliner Dampfbäckereien (Berlin steam bakeries) came into business, and registered the Trademark for "Berliner", and so only backers who were trained in the specialty in Berlin were permitted to use the term "Berliner."

All of that information beside, the sentence is also very clearly grammatical to anyone who speaks German fluently. The use of "ein" in the sentence was for a dramatic, strengthening effect. But, as this story is already very widespread, there is a lot of revisionist history keeping the idea going.