It's raining cats and dogs.
It's raining hard.
Multiplication is a "piece of cake."
It is not hard, it's easy!
Break a leg.
Good luck!
It costs an arm and a leg.
It's expensive.
He is feeling "under the weather."
He feels sick.
Don't let the cat out of the bag.
It means don't tell the secret or don't ruin the surprise.
She is "catching some Z's."
She is sleeping.
You're pulling my leg.
You're joking.
You can say that again!
I agree!
Hit the sack.
Go to sleep.
He got up on the wrong side of the bed.
He's grouchy.
Hitting the books.
Studying hard.
Don't "throw in the towel!"
Don't give up!
Let's pig out!
Eat a lot!
Give it a shot.
Try it.
In hot water.
In trouble.
