in article , C J Campbell at
wrote on 11/14/03 6:01 PM:

He did claim to be a jelly donut (literal translation of "Ich bin ein
Berliner")

The editors of several Berlin newspapers would be surprised to hear that
(Berliner Morgenpost, Berliner Zeitung, etc.). Berliner refers to a resident
of Berlin, just as a Hamburger is a denizen of Hamburg and a Frankfurter
resides in Frankfurt. Generally, these words are only funny to non-Germans
who haven't the slightest idea what they're talking about.