Manhattanite

This does not take into account the tens of thousands of New Yorkers who are harmlessly and charmingly insane in a peculiarly Manhattanite manner.

Walter Gaskell was a tall, silver-haired Manhattanite with a narrow waist and broad shoulders, and his blue eyes had the luminous, emptied-out look of a reformed alcoholic's.

The most likely explanation is that Cage imagined Peter as a fop of the first order, the type of ivory-tower Manhattanite whose exalted sense of privilege naturally leads to a hilariously affected manner of speech.