Slangs
The first one “break a leg”
This phrase was originally from the ancient Superstition. It was said that if they wished each other something bad, good might happen. So when you hear "break a leg," it&`&s really means "do well." Also, it can mean to work really hard at something.
For example:
Break a leg in your test today
(祝你今天考试好运气)
The second one “pull one’s leg”
Pull p-u-l-l,是“拉”的意思pull one’s leg从字面上看就是“拉某人的腿”,这可不是中文里所谓“扯后腿”的意思。
Actually here it means someone just kidding! "You&`&re pulling my leg." 意思相当于“你是在愚弄我吧!”或是“你是跟我开玩笑的吧!”
For example
A: Are you really going to Italy this winter?
B: No way. I’m only pulling your leg and you believed it?
A:你真的今年暑假要去意大利吗?
B: 哪有可能? 我只是跟你开玩笑的, 你还当真啊?
需要注意的是 pull one&`&s leg,而不是 pull one&`&s legs,试想你同时拉一个人的双腿他不就跌倒了吗?所以只能拉一条腿 leg 不能拉两腿legs!但是 "You are pulling our legs."则是正确的用法,因为它的意思是“你在愚弄我们”。