"throw a curve" in Chinese (Simplified)
出其不意让某人措手不及（表达）
Definition
用让人意想不到或棘手的事情让某人吃惊，特别是对方没有准备的问题或情况。
Usage Notes (Chinese (Simplified))
主要为美国口语表达，来自棒球术语，更常见的形式是 'throw a curveball'。用来表达给人带来意外或难题，通常不是正面的惊喜。
Examples
The teacher threw a curve during the quiz.
老师在小测验时**出其不意**了。
Her question really threw a curve at me.
她的问题真的让我**措手不及**。
They threw a curve when they changed the plan suddenly.
他们突然改变计划时，真是**出其不意**。
My boss threw a curve in the meeting with an unexpected question.
老板在会议上用一个意外的问题**让我措手不及**。
Life can throw a curve when you least expect it.
生活总会在你最意想不到的时候**让你措手不及**。
Just when I thought everything was fine, the news threw a curve at us.
就在我以为一切都很好时，这个消息**让我们措手不及**。