Alberto Ruiz Gallardón, then major of Madrid, plays his own great-uncle, composer Isaac Albéniz, at his own request: When director José Luis Garci approached the town hall of Madrid to get their consent to film there, he showed the script as a proof; after reading the script, the Major phoned Garci, asked if he had already casted Albéniz, and offered to play the role himself.
Although Holmes talks often times with Mrs. Hudson when he's in his London's house, she never appeared in screen.
Irene never calls Sherlock by his birth name, but naming always "Scott".
Despite of previous incarnations of Sherlock Holmes, Gary Piquer never wears the typical Holmes' costume but the pipe.
For the scene of the travel from London to Madrid, are used some old pictures what recreate some places like London's streets and port, Paris and finally Madrid.