Memory Game Idioms 2Online version Players will try to match the idiom with it's meaning. by Lunarn Smith Let the cat out of the bag Can’t stay calm (relax) because you’re nervous Work until late at night Hold your horses Tell a secret Very expensive Burn the midnight oil It’s not rocket science Good idea or invention It’s not hard. Let sleeping dogs lie Best thing since sliced bread Happens very rarely; uncommon Once in a blue moon Cost an arm and a leg Ants in one’s pants Don’t start problems or cause trouble Wait and be patient