"You've got to be kidding!"
Meaning: You can't be serious! (What you said can't be true. What you said is very surprising/hard to believe.)
Tonyang: Haven't you heard the news? Agua's alive!
Doña Amalia: You've got to be kidding!
Last week's idioms:
on time
pooped
rain cats and dogs
shoot the breeze
toss (something)