Murdoch is a large orange freight engine in Thomas & Friends, the long-running British children's series based on The Railway Series books. His whistle is one of the many distinctive engine sounds collected by fans, who clip individual whistles, horns and theme cues for edits, quizzes and soundboards. Because each Thomas engine has its own tone, Murdoch's whistle is often used to identify him instantly in fan videos, even without showing the character. It remains popular with railway enthusiasts and viewers who grew up watching the show.