I have a memory of one mid-run episode where a woman in Luke's Diner is asking Lorelai about Luke, and one of her questions is "So he's Jewish?" And Lorelai responds with "No -- well yes he is but that's not the point" before going on.

Does anyone else remember this? Or have any idea what I might have in mind?

EDIT: FOUND IT but it's a let down. Season 4, episode 12. Jason says that he and Lorelai should go to "Duke's," and Lorelai says it's closed because it's 8 am on a Friday. Jason asks why, and Lorelai says it's the sabbath. Jason says "Duke is Jewish?" And Lorelai says "No, Luke is Jewish."

Sadly, this doesn't corroborate anything. We know Lorelai is lying about Luke's being closed, and, as Jason promptly points out, shabbat doesn't start until sundown. My conclusion is that Lorelai is lying across the board. Womp womp.