It Is Raining Cats and Dogs

It is raining very heavily

Savvy

Having practical knowledge or understanding; shrewd

Cost an Arm and a Leg

Something that is very expensive

Catch Someone with Their Pants Down

To discover someone in an embarrassing situation

Go Bananas

To become very excited, angry, or crazy

Cry over Spilt Milk

To be upset about something that has already happened and cannot be changed