Codspiker

Codspiking - The act of throwing a fish finger (cooked or otherwise) into another persons alcoholic drink without the drinkers knowledge. People usually do this as a prank to get someone annoyed/irate for comical value.

If that Codspiker Kev is Codspiking again, I ain't coming to your party.

Or...

Richard was Codspiked last night, he smelt of fishy Birdseye fingers all night.

Or...

What the hell is floating around in my beer...oh mate, you been codspiked again, 3rd time this week!!