a leopard never changes its spots

proverb One will stay true to one's nature, even if one pretends or claims otherwise. After our breakup, he came crawling back, trying to convince me that he'd changed—but I know that a leopard never changes its spots. You're never going to convince Tom about this—he's too stubborn, and a leopard never changes its spots. A: "Come on, a leopard never changes its spots." B: "I thought so too, but the former president really seems to have changed his views on social welfare since leaving office."