Natasha, there are also many interesting threads here in Mudcat which might well provide you with starting points. Two which I remember intrigued me are "Froggie went a courting" which started off life as, if my memory seves me, a sixteenth century Scottish, political satire and Lord Randall, which morphed into many songs most notably "Where have you been all the day Billy Boy"

While many, if not most of the versions of the frog's wedding have become just another beatrix potter tpe kid's animal story you don't have to look far for the original xenophobic warning. When Leadbelly concludes with "There'll be no tadpoles all covered in fur" you can hear the old gossips say " I'm telling you no good will come of it." The song has crossed the ocean and been used in diverse cultures for the same old message.