Sherlock Holmes is an English detective made famous in a series of novels and short stories by Sir Arthur Conan Doyle. It is unclear how Holmes came to be in the twenty-first century, or even how he came to life at all, but it likely had something to do with the actions of the time goddess Chronotempia in Episode 26.
Holmes is a passionate crusader for the cause of literary rights and representation. He murdered Hobo Joe and framed Geek Slice for the act in hopes that investigation of the crime would give increased exposure to literary characters such as himself. Although the Crypt-Dwellers mostly forgave Holmes' dastardly deed and agreed to feature public domain literature more prominently in the future, Hobo Joe reappeared as a vengeful ghost and terrified the detective. Holmes fled above-ground and has not been seen since.