"You are pulling my leg!" means...
"You are kidding/teasing me!"
"I'm all ears!"
I'm listening.
"It's raining cats and dogs"
It's raining a lot./It's pouring.
"I'm on top of the world!"
I'm very excited, very happy.
"I need to sleep on it."
I need to think about it.
"I have butterflies in my stomach."
"Your head is in the clouds."
You're very distracted or daydreaming.
"I am dog tired."
I am exhausted.
"Don't throw in the towel!"
Don't give up! Perservere!
"You are going to catch some z's."
You are going to sleep.
"It went in one ear and out the other."
You weren't paying attention or listening.
"You have a heart of gold."
"After I got home yesterday, I took a cat nap."
What is a cat nap?
A short nap
"He got up on the wrong side of the bed."
He's in a bad mood.
"Hit the books!"
Go study!
"Stay on your toes!"
Stay alert, be ready to do what you have to do
"Ugh, an arm and a leg, but it was worth it."
What does "an arm and a leg" mean?
It was very expensive.
"Hold your horses."
Be patient, wait, don't rush.
"I'm down in the dumps."
I'm depressed, sad.
"You are a couch potato."
You are very lazy/watch too much TV.
"He has a green thumb."
He is good at gardening.
"You put your foot in your mouth."
You said something you shouldn't have (that was inappropriate).
"Don't let the cat out of the bag."
Don't ruin the surprise/tell the secret.
"I'm nuts about you/it."
"You are in hot water."
You're in big trouble.