Brothers Kipper

Two Derry men were on their way to a fancy-dress party, dressed as herrings, when they decided to step into a pub on the way for a pint.
They sat at the bar for a while, and then one of them got up and walked out the front door without finishing his pint.
When he hadn't come back after ten minutes, the barman came over and said: 'Hi, where's your mate vanished to?'
'How should I know?' replied the other Derry man. 'Am I my brother's kipper?'