Two features of the pronunciation of the Berlin dialect of German are very striking. They are the pronunciation of the consonant written g in standard German (but pronounced as if written as j) and of the diphthong written ei (but pronounced as if written as ee).
Consonant written g
In the Berlin dialect, the consonant g is generally (especially at the beginning of a syllable) pronounced like German j (English y). So the greeting Guten Tag (good day) is pronounced as if it were written Juten Tag.
I first heard of this feature on a school exchange in Frankfurt am Main in 1973. My exchange partner’s class were reading a well-known play called Der Hauptmann von Köpenick (The Captain of Köpenick), which is set in Berlin. The dialogue attempts to capture the dialect and the script conveys this by replacing the character g with the character j. This replacement has a pervasive effect, not least because most past participles in German include the prefix ge- (for example: gewesen = been; gehabt = had).
Diphthong written ei
I came across another feature of the Berlin pronunciation on visiting the city in 1976 for the first time. I spent 3 weeks working on a project building an adventure playground.
While there, I made a few trips on the Berlin Underground (U-Bahn). At each stop as the doors were about to close, the train guard would announce Zurückbleiben (stay back). They would invariably pronounce this as if it were written zirickbleeben. The diphthong written ei sounds in standard German like the English word eye but they pronounced it like a long version of the first part of the diphthong in English day. This replacement wasn’t isolated, but seemed to occur systematically in every word containing this diphthong.
In fact, the pronunciation of the word Zurückbleiben also shows another replacement which I remember as typical of Berlin in the 70s: i instead of ü in the second syllable and to my ear also i instead of u in the first syllable. But maybe that last replacement was just in this particular word because of the influence of the i in the second syllable, a phenomenon know as regressive assimilation or anticipatory assimilation.
Recent developments
I have visited Berlin half a dozen times since then, mostly since German reunification. These Berlin dialect features seem much less prevalent now than they were in 1976. Presumably, this change has been caused by a large influx of people from other parts of Germany.
Hauptmann von Köpenick
Der Hauptman von Köpenick is a play written by the German writer and dramatist Carl Zuckmayer (1896–1977) in 1931. It is based on the true story of an ex-convict who in 1906 acquired a military uniform and, passing himself off as an army captain, imprisons the mayor of the Berlin district of Köpenick and makes with money from the town hall. One theme of the play is the danger of blind deference to authority (symbolised by the uniform).
The incident led to the coining of the German term Köpenickiade, to describe a confidence trick carried out by impersonating a high-ranking person, perhaps partly by misue of a uniform.
Similarly, the English short story writer Saki used the verb to koepenick and (the noun koepenickery) in 1911 in his short story Ministers of Grace, defining it as ‘to replace an authority by a spurious imitation that would carry just as much weight for the moment as the displaced original in his short story’.