throw someone a curve

(verb) to do something unexpected to someone

Example Sentences:

Girlfriend: I have some news.
Boyfriend: Okay.
Girlfriend: I don’t want to throw you a curve, but I’m moving to Los Angeles.
Boyfriend: Great! Can I come with you?
Girlfriend: Nope.

The boss threw me a curve when he announced that I was getting a raise.

I had a lot of difficulty with my Homestay Mother, because she was always throwing me a curve by coming in to clean my room at strange hours of the day.

From the Blogs:

Eagles throw Giants a curve with ground game

Media:

Similar idioms:

1. come clean
2. throw in the towel
3. throw cold water on
4. throw up
5. spick and span
6. the elephant in the room
7. douche
8. asshole
9. ass
10. douchebag
11. d-bag
12. lame