Half Man Half Biscuit
An e-mail was sent into the show promoting the band 'Half Man Half Biscuit'.
Karl only saw the name from over Steve's shoulder and genuinely believed there was, in fact, a person who was born half man and half biscuit. Karl then offered the advice "Never go swimmin'."
This was in Show 80 (12-06-2003), starting at 24:23.