 The Doctor also wears a one @-@ off costume , Victorian @-@ themed , which Smith described as " a bit <unk> <unk> meets the Doctor " . Moffat described the new outfit as a " progression " as the Doctor was in " a different phase of his life now " and felt more " grown @-@ up " and <unk> . The costume was designed by Howard <unk> for this episode . " The <unk> " also contains several references to Sherlock Holmes , including the Doctor dressing up as him . Moffat is co @-@ creator of the BBC series Sherlock , for which Smith auditioned for the role of Doctor Watson before being cast as the Doctor . In addition , the incidental music during the scene bears a resemblance to the Sherlock theme . 
