I agree that there are only a certain number of "joke" or "gags" in the world, but it annoy's me when someone doesn't even bother to try and change it that much, and just hopes that no one has noticed. Even when asked why did they choose a certain group of the community, in this case Jewish people, they come up with some kind of history saying "Jews...Why not. Have always had an affinity since my days at school in Kenton, Middlesex [ Anyone who knew Kenton, NW London in the early 80's, will know what I mean ]"
Just be honest and say "because they were already jewish in the joke to begin with "