This post contains incidental dialogue spoilers for The Hounds of Baskerville (episode two of the current Sherlock series) but I'm not putting anything behind a cut because it's one of the lines taken from the original stories. If you care anyway, THIS IS YOUR WARNING.
(Or I could have just put it under a cut and avoided all this but WHATEVER.)
So. In the latest episode of Sherlock, the title character said a line many people will have recognized as from the original stories: "When you have eliminated the impossible, whatever remains, however improbable, must be the truth." In the EXACT SAME CONVERSATION, John jokingly refers to Sherlock as "Spock".
Spock, in both the more recent film and one of the earlier ones
quoted this same line and attributed it to one of his ancestors.
There are other Sherlock Holmes references in various iterations of Star Trek which would necessitate the Sherlock in-universe version of Trek canon to be different, of course. This one, however, stuck out for me because Conan Doyle (or Holmes??) is meant to be Spock's ancestor and yet John just called Sherlock "Spock".
If John hadn't done so so close to Sherlock saying that line, I may not have even noticed. Am currently developing a conspiracy theory wherein Gatiss did this intentionally in order to break nerds' brains.