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You can't get a leopard to change his spots. In fact, now that I come to think of it, you can't really get a leopard to appreciate the notion that it has spots. You can explain it carefully to the leopard, but it will just sit there looking at you, knowing that you are made of meat. After a while it will perhaps kill you.

"Less Than Three Years: A Policy Revision". itre.cis.upenn.edu. January 04, 2007.
You can't get a leopard to change his spots. In fact, now that I come to think of it, you can't really get a leopard to appreciate the notion that it has spots. You can explain it carefully to the leopard, but it will