Throw someone a curveball Informal

To confront someone with an unexpected challenge, question or change that disrupts their expectations or plans.

A curveball is a baseball pitch designed to change direction in flight and mislead the batter. The figurative expression transfers that element of surprise to unexpected questions, setbacks or changes of plan. Someone who is thrown a curveball must adjust quickly because the situation does not develop as anticipated. The idiom is especially recognizable in American English, where baseball supplies many everyday metaphors. Unlike a literal pitch, the figurative curveball may be thrown by circumstances rather than by another person. Its central idea is not simply difficulty, but difficulty arriving in an unexpected form.

The client threw us a curveball by changing the deadline overnight.

That interview question really threw me a curveball.

Life threw her a curveball just as things were improving.