We Sherlockians all know that this quote originated with Sherlock himself in The Sign of Four. But, the Sherlock Holmes novels don’t exist in BBC Sherlock’s universe. So, for the longest time I just assumed that Sherlock came up with the phrase in The Hounds of Baskerville at The Cross Keys pub, and that John’s “Spock” comment was just poking fun that Sherlock was being overly analytical and needed to calm down.
However, then I obviously remembered that the phrase was actually said by Spock in the 2009 film Star Trek. And that The Hounds of Baskerville takes place in 2011.
So, assuming that BBC Sherlock exists in a universe in which Sir Arthur Conan Doyle and his stories don’t exist, Sherlock is actually quoting Spock (who coined the phrase) from the 2009 Star Trek film- not just coming up with something clever off the top of his head. And John recognizes that and calls him out on it. So this means that they’ve both seen the film. I’d wager that they saw it together. Sherlock doesn’t seem like much of a film buff, but he’d endure it if he saw it with John.
Meaning that at one point in time John and Sherlock had a Star Trek night.
That is all.