10 Greatest Cold Opens In Doctor Who
2. The Bootstrap Paradox - Before The Flood
Peter. Capaldi. Monologuing.
Those three words alone are enough to justify the inclusion of Before The Flood on this list, but I'm contractually obliged to write a bit more than that.
The occasional fourth-wall breaking of the Twelfth Doctor was one of the most fun traits of his incarnation, and here we are treated to two unadulterated minutes of Twelve chewing the scenery as he speaks directly to the viewer, explaining the concept of The Bootstrap Paradox.
He tells a story about a time traveler who travels back in time to meet Ludwig van Beethoven, only to find that Beethoven doesn't exist. This mysterious time traveler (who definitely bares absolutely no resemblance to anyone the Doctor knows) decides to publish Ludwig's work himself, and as a result he becomes Beethoven. This story, of course, is of direct significance for the episode yet to come, in which The Doctor only says a list of names because he heard his future self say it, and his future self only said those names because he too had seen his future self say it, and so on. Wibbly wobbly...
The Bootstrap Paradox has been used a number of times in the show, and every time viewers it has left viewers a little baffled, so this short crash course was a wise addition - and the way in which it's explained almost makes it seem like it makes sense (though best not to overthink it, as it's still an impossibility).
In addition, having a self-contained cold open that doesn't run into the episode at all is such a unique and refreshing approach that really makes this stand out.
The sequence is capped off by Twelve posing a question: Who really composed Beethoven's fifth? The question is left unanswered, because, well, there is no answer. As the cogs whir away in your brain, The Doctor plugs in his electric guitar (which, contrary to common opinion, is absolutely the coolest accessory the Doctor has ever had) and strums out the chords to the classical piece in question, before launching into a rock version of the main theme, played by Peter Capaldi himself.
In summary, this cold open is just about the most Twelve that Twelve has ever been, playing to every strength of both the character and actor. It's iconic stuff.