A storm in a teacup is a big fuss made about something of little importance.
Examples of use:
1. My brother and sister had a big argument about the television yesterday, but it was just a storm in a teacup.
2. News items:
a) In a case of a legal storm in a teacup, police forced a stunned magistrate to deal with a man accused of damaging a $3 plastic cup.
b) Gordon Brown dismisses leadership challenge as storm in a teacup.
3. The workers say they will work-to-rule, but we think it's a storm in a teacup.
Image © Juliana Coutinho