Moriarty calls the computer "Mr. Computer" even though the ship's computer clearly speaks in a female voice.
After Moriarty gives the sketch of the Enterprise to Data, Geordi asks, "What's wrong, Data?" Data hands him the page. Geordi says, "Data, this is impossible," and he flips the paper over so that it faces the camera. At this point we see the drawing right-side-up, which means that Geordi was looking at it upside down.
Trivia: In this episode, Picard utters a profanity other than the usual "damn" or "hell" we see in most Trek series, saying "merde" in response to finding out that Moriarty was programmed with skills that would defeat Data. "Merde" is a French word that translates in English to a 4-letter word for excrement.
After the first holodeck adventure, Geordi tells the computer to freeze-program, but the fire keeps burning in the fireplace.
Data says Holmes defeated Moriarty only at the cost of his own life. That's not correct; because of the outcry by Doyle's readers over the great detective's death, Holmes "survived" the fall at Reichenbach Falls and returned in "The Adventure of the Empty House."
Data: We shall return to the holodeck where I shall dare it to defeat me. And you, madam, are invited to be a witness.
Dr. Pulaski: I wouldn't miss it.
Dr. Pulaski: To feel the thrill of victory, there has to be the possibility of failure. Where's the victory in winning a battle you can't possibly lose?
Data: Are you suggesting there is some value in losing?
Dr. Pulaski: Yes, yes, that's the great teacher. We humans learn more often from a failure or a mistake than we do from an easy success.
Wil Wheaton (Wesley Crusher) does not appear in this episode.
Professor Moriarty returns in the Season 6 episode "Ship in a Bottle."
Referencing the phrase "Elementary, my dear Watson," commonly attributed to Sherlock Holmes in the stories of Sir Arthur Conan Doyle. In fact, the phrase never appears in any of the author's works. The only time Holmes ever uses something similar is in "The Crooked Man," when he simply tells Watson, "Elementary."
Sherlock Holmes Stories
Asked to create a Sherlock Holmes mystery for Data, the computer combines elements from two Holmes mysteries. Jabez Wilson and The Red Headed League are, of course, from The Red Headed League, but the murder method (sending a venomous snake down a bell cord) is from The Speckled Band. The first mystery (the one chosen at random at the beginning) is A Scandal in Bohemia.