“Who?”

You're talking with your wife. She says, "Guess who I saw today!". You respond:

Who?

Who?

This is the standard response when someone says "Guess who..." You might think that you're really supposed to try to guess who the speaker is talking about, but you're not. The speaker just wants you to ask "Who?"

If the speaker says "Guess what..." you should answer:

What?

...and so on. There are also other silly answers that you can give if you want to joke with the speaker:

A: Guess who I saw today!

B: Barack Obama? (Or you can use any other name of someone who's extremely famous, or lives in another country, or isn't even a real person.)

A: Guess what?

B: Chicken butt. (This doesn't really mean anything. People just say this because it rhymes and sounds silly.)