将以下英文短语翻译成中文。


"once in a blue moon"，"raining cats and dogs"，"let the cat out of the bag"，"break a leg"
"once in a blue moon" - 很少发生的时候
"raining cats and dogs" - 瓢泼大雨
"let the cat out of the bag" - 泄密
"break a leg" - 祝好运（尤其是演员演出前的祝福用语）