throw someone a curve

From the curve ball in baseball, where a spin is employed to adjust the path of the ball unexpectedly.

throw someone a curve

1. (baseball) Used other than with a figurative or idiomatic meaning: To pitch a curve ball.
2. (figuratively) To surprise; to introduce something unexpected or requiring a quick reaction or correction.

   He really threw me a curve when he asked me a personal question at work.

• throw for a loop
• bowl a googlie