butter wouldn't melt in sb's mouth “butter would not melt in one's mouth”是英文习语，一般用来形容人表面上极为恬静一本正经，非褒义。 used when someone looks as if they would never do anything wrong, although you feel they might 描述这个人看起来似乎永远不会犯错，但是你感觉到其实并不见得 Tommy