At the last minute, I threw them acurve ball by saying, "We're going to bring spouses."
在最后一刻，我给了他们一个惊喜，说：“我们会带配偶。”
《柯林斯英汉双解大词典》
2
4：The salesman threw me acurve when he told me it was a real bargain, but he didn't say that the camera was a discontinued model because of its inbuilt defect.
那售货员骗他说照相机真是价格低廉，但是他却没说那相机由于构造上的缺陷所以是停产型号。 他话里的threw somebody a curve 意思是耍花招骗人。
3
2：The professor threw us acurve: half of the questions were from the reference book he asked us to read but we never did since he didn't cover the book in class.