A fox may grow gray, but never good.
狐狸有可能會變灰，但絕不會變好。
gray 灰色的 grow gray 變灰
A leopard can't change its spots.
豹子不能去掉它身上的斑點。
leopard 豹子，美洲豹 spot 斑點
You cannot make a crab walk straight.
你不能讓螃蟹豎着走路。
crab 螃蟹
old habits die hard
積習難改
He's taken up smoking again. You know he had quit for about a year, but Iguess old habits die hard.
他又開始抽菸了，之前他已經戒菸大約一年多了，可能還是積習難改吧。
