Herbert the Turbot?

          "I was once offered a princely sum," went on Psmith, now floating happily along on the tide of his native exuberance, "to write a ballad for the Fishmonger's Gazette entitled, 'Herbert the Turbot,' But I was firm. I declined.
          "Indeed?" said Lord Emsworth.
          "One has one's self-respect," said Psmith.
          "Oh, decidedly," said Lord Emsworth.

(from Leave It To Psmith, by Sir Pelham Wodehouse)