I remember hearing something about JK twitter-confirming that the Goldstein in the original books was of Jewish ancestry, I think? Either way, put a Goldstein in New York in the 1920s? That's all I need. 'Kowalski' as a name could be Jewish or not, but given the actor, a bakery and his grandma's picture on the wall? Nope, that's a good Jewish boy right there. XD