Pardon my French
粗俗語
It's a light hearted attempt at apologizing, usually used around people you know well but don't want to risk offending with bad language.
不是一個很走心的道歉，通常是你對你很熟悉的人，然后不想冒險直接說一些不好的話。就可以加上這個表達。

Going Dutch
AA 付賬

Fly on the wall
偷聽講話的人
I wish I could be a fly on the wall in that situation!
我真想偷聽，聽聽是啥情況。

A perfect storm
一場完美的風暴 （各種不幸的小事一起發生了）
The football match was cancelled due to a perfect storm of events, the bus was late, the referee couldn't make it and it started to snow too!
這個足球賽取消了，英文各種不幸的事情，車晚了，裁判員到不了，還下雪了！

At the drop of a hat
毫不遲疑的
He used to be very shy, going red at the drop of a hat.
他曾經很害羞，動不動就臉紅。

An arm and a leg
很貴
Living in London costs an arm and a leg.
居住在倫敦的小費太高了。