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