I've heard the punchline to many jokes "funny, doesn't look Jewish".
I've also heard jokes about the joke, like Mel Brooks' Spaceballs comment "funny, She doesn't look Druish" which implies the phrase is well-known, at least in Jewish circles.
I'm wondering what the origin of this phrase is. I'd also like to know if it is perjorative or possibly a joke about a perjorative statement.
Anyone have any information?
I think this line is so old that it's a challenge for a comic to make a new joke with the old punchline. I've heard several jokes with this punchline, most of which have some implied reference to circumcision. But the one I hear most, which seems like it may be the original is this:
A man was riding a train when a woman from a seat further back came up to him and asked if he were Jewish.
"No, I'm not Jewish", he replied.
Several minutes later she came up again and said, "Are you sure you're not Jewish?"
"I'm absolutely sure I'm not Jewish", he said.
A while later she comes again and says, "I hate to bother you, but are you positive that you're not Jewish?"
"Yes, I am absolutely positive that I am not Jewish", he said again.
This happened several more times until the man in frustration finally said, "Okay, I'm Jewish. Does that make you happy?"
To that the lady said, "Funny, you don't look Jewish".
I think the root of the humor is that, in western countries, there is nothing definite to distinguish a Jew from any other Caucasian. In the middle east Jews look like every other middle eastern person. Yet some seem bent on picking out Jews. Who knows?
It's a racist saw, of which there are many, easy to mock.
Not that there's anything wrong with that. Some of my best friends are racist. They're really successful for racists. You would never guess they were racist.[edit: added the following]
I think the specific line "Funny, you don't look Jewish" may have been popularized by a joke, mocking similar statements stemming from a very real racist obsession with looks and Jewishness. I can find examples of variations on that statement and questions about "looking Jewish" at least as far back as 1875 with direct connection to prejudice and racism, or fear of same.