Trivia: At the beginning of the episode (at about 08:26), when John arrives at the empty junkie house and opens the back of his car, a large billboard can be seen behind him. The largest words on the ads present on the billboard form a phrase 'Information is the power', which also the main theme of this episode.
During the final scene, while in his car, Mycroft is holding his phone in his bare hand when he gets the call about Moriarty. However, when he steps out of the car, still on the call, his hand is gloved.
Trivia: According to Magnussen's data, Mrs. Hudson's maiden name is Sissons, she's a semi-reformed alcoholic, and a former "exotic dancer."
When John first sees Sherlock's body, there is a large truck with red and yellow markings blocking part of his view. The truck vanishes completely when John is hit by the biker and Sherlock can now be seen surrounded by several people. In the overhead shot of Sherlock, the truck can be seen driving off and people are only just now beginning to rush to Sherlock.
The "Sherlock's a Fake!" article that Kitty shows John consists of the same couple of paragraphs repeated three times across the four columns.
The article entitled "Jewel Thief on Trial at Bailey" repeats one of the sections twice: "Irish born Moriarty...trial of the century" is followed again by "Irish born Moriarty..."
Trivia: The opening dialogue establishes that 18 months have passed since the events of "A Study in Pink," matching the real-life time that has elapsed.
The newspaper articles that show Sherlock in the deerstalker hat have errors. The first repeats the second paragraph twice, beginning mid-sentence. The same paragraphs appear again in the first column of the third article, even though they are clearly meant to be distinct.
There is a discrepancy about the age of Connie Prince. On the diner's television, the caption on her death reads, "Make-over Queen Connie Prince dead at 48." In the next scene at the morgue, Lestrade reads from a file and states that Connie was 54.
DI Lestrade refers to the five tones (four short and one long) heard on the pink phone as "the bloody Greenwich Pips." However, the Greenwich Time Signal (a.k.a. "the pips") has six tones (five short and one long) and are used to indicate the top of the hour. The bomber intentionally removed the first pip from the recording so there would be only five (allowing the connection with the secret societies warning).
The dead man, West, is referred to as "Andrew" throughout. However, in the end credits, his first name is listed as "Alan."
Dan Brown's novel The Lost Symbol can repeatedly be seen briefly during this episode. Its plot revolves mainly around symbols and codes, thus sharing a theme with this episode.
When Sherlock and John are first seated at Angelo's restaurant, Angelo brings a candle for the table. In the next shot for John's conversation with Sherlock, John is chewing, although neither of the two placed an order for food, nor did we see Angelo bring anything else to the table. In the next full shot of the tabletop, we see an entre for John, a glass of wine, and a cup of tea before the two leave the restaurant.
The newspaper article seen four minutes into the episode about the dead student has multiple repeating paragraphs: the first paragraph from the first column matches the second paragraph in the third; also, the last five lines of the second column are repeated in the beginning of the third column.