Don’t you think the title sequence to Sherlock would be a good place to hide subtext? Well, let’s have a look at one detail (I already talked about the Gherkin in the title sequence here): the blood.
The title sequence ends with a few shots of a petri dish with blood and a chemical reaction that’s part of a forensic analysis of the blood.
Due to the position of these shots at the end of the title sequence, I suppose a) they’re important and b) they tell us something about Sherlock.
On a literal level, they show a substantial part of Sherlock’s work, i.e. chemical experiments and forensic analyses.
But there’s more to it: the blood seems to boil when the reagent is added. This could be part of the idea of “solving crimes as a metaphor for sex” (see LSiT’s meta on A Study in Pink): solving crimes excites Sherlock, it stirs his blood.
But I think we can take the subtext even further. The blood Sherlock analyses in the scene these shots were taken from is Ian Monkford’s. Those are the original shots in The Great Game (33:26–33:32):
Remember? Ian Monkford’s blood had been frozen before it was applied to the abandoned car (that’s one of the things Sherlock found out by his analysis). Anticipating the possible objection that “frozen blood” might refer rather to Mycroft, the “Ice Man”, than to Sherlock, let me answer: Yes, that’s right. But the show is called “Sherlock” and not “Mycroft”, and therefore I’d argue that the title sequence tells us something about Sherlock, not about Mycroft. Then again, Sherlock can be rather frosty himself.
The name of the man whose blood Sherlock analyses from is telling: Monkford. A monk is someone who – like Sherlock – has chosen to lead a celibate life. But as for Sherlock, his celibate life gets disturbed. Something or someone makes Sherlock, the cool and (sometimes) seemingly asexual man who is “married to his work” become hot-blooded and passionate. Guess who that someone is. I’ll just mention the drop lingering on the pipette’s tip for ages and leave you to your own deductions.
(Another possible objection: It’s Sherlock himself who adds the reagent to the blood, not John. Yes, right again, but Sherlock has chosen to let John enter his life. He has chosen to include John in his detective’s work. And (again, see one of LSiT’s amazing metas) during the best man’s speech he’ll deduce himself into being in love with John.)
So, to cut a long story short: The shots of the blood in the title sequence show Sherlock’s sexual awakening triggered by John in a nutshell. They are the culmination of the title sequence, so we can safely assume that’s what the story is heading for and has been from the beginning. Long live TJLC!