When I was in college, I had a group of friends from all over the country. We did a lot of things together, drinking, dating, etc.. Two of them were Jewish and I didn't even know it for 3 or 4 months after getting to know them. I didn't ask what religion they were and they didn't say. One day, I don't know if it was something I said or what but one of them stated, "You know we're Jewish don't you?" I said, "No." The other one said, "Well, we are." I said, "So." There was a few seconds of silence and things went back to the same as always. The subject never came up again.
Reminds me of Cramer and the "anti dentite" bit.