Giant Rat of Sumatra

The Giant Rat of Sumatra is a fictional giant rat, first mentioned by Arthur Conan Doyle in "The Adventure of the Sussex Vampire". As part of the tale, the protagonist, Sherlock Holmes, declares that there is a "story" connected with this rat, presumably a detective case he has handled. The name of the rat and its implied unpublished history were later used in works by many other writers.