A preview segment gives away a bit of a spoiler from the BBC drama's third series finale, with Murray transforming into "Murray-arty" insisting the Brit was really the famed detective.
"Murray, I don't really have an arch-nemesis in real life," Cumberbatch explains.
"Well you do today, and his name is Murray-arty!" the puppet shouts, letting out a worthy cackle. "Are you ready for my brain-bending challenge, Sherlock?"
Murray-arty won't hear of it when the actor tries to explain that he's not actually the character he plays on TV, and insists Cumberbatch solve a puzzle. Cumberbatch enlists the help of Count Von Count, and together, they solve The Sign of Four (or is it Three?)