Sherlock Hemlock is a Muppet spoof of Sherlock Holmes, as seen on Sesame Street. Sherlock is the self-appointed "World's Greatest Detective," dressed in the iconographic Holmes deerstalker cap and Inverness cape, and usually brandishing a large magnifying glass. He prides himself on his powers of observation and does succeed in deciphering small clues, but he seldom arrives at a correct, final solution without assistance. When he does find a clue, he often shouts, "Egad!" He speaks with a British accent and his earliest appearances were often signaled by "detective music" (as Ernie called it), a series of dramatic stings on a piano.
Hemlock also appeared in the recurring Caveman Days sketches as "The Royal Smart Person."
Though generally one of the less musical Muppets, Hemlock sang "X Marks the Spot!", a dire warning of what the letter/symbol X may signify, first on The Muppet Alphabet Album and then on the series itself.
In Season 21, Sherlock Hemlock starred in all of the Mysterious Theater segments, and by this time he he was given a sidekick of sorts: a faithful dog named Watson, who joined his master in the segments and occasional street appearances. Most notably, in Episode 3033, Sherlock and Watson try to find Maria's sock on a laundry day in her basement, accompanied by the Mysterious Theater theme and host Vincent Twice.
Sherlock's last major appearance occurred in a Season 27 episode (Episode 3424), where the letter X wanted to quit the alphabet. After this, he was only seen in old sketches until the early 2000s. Then, in 2010 for the show's 40th season, Sherlock reappeared on Sesame Street in a brief speaking cameo at Hooper's Store in Episode 4206.
According to Sesame Street Unpaved, Nelson's performance is based on Basil Rathbone's famous portrayal of Holmes in the 1939 movie The Adventures of Sherlock Holmes and its early 1940s sequels. However, the voice, particularly in the early sketches, is modeled after the clipped diction of another British movie star, Ronald Colman.