Sherlock Holmes trip back in time required Benedict Cumberbatch, Martin Freeman and co to undergo quite the transformation, but did you spot the nods to the modern day series and Sir Arthur Conan Doyle's novels dotted around the special?
We gave up our opportunity to pig out on the sofa on New Year's Day and headed to Leicester Square to catch the show on the big screen, where we clapped eyes on an exclusive featurette presented by co-creator and writer Steven Moffat.
The sneak peek behind the scenes took us through the Victorian era 221b Baker Street, as Moffat pointed out some little Easter eggs hidden around the apartment.
How many did you spot?
The jackknife in the unanswered correspondence
A feature of almost every single Sherlock Holmes story or adaptation, Sir Arthur Conan Doyle even featured it in the stage directions for The Adventure of the Speckled Band. It's little wonder, then, that Moffat and Gatiss chose to include it in The Abominable Bride.
The unframed portrait of Henry Ward Beecher
The original stories note that Holmes was a big fan of the American Congregationalist clergyman, social reformer, and speaker. And so when dressing the set for the special the powers that be opted to include the unframed portrait of him that's mentioned in the original tales.
The skull in the sitting room
Modern day Sherlock's 221b Baker Street bachelor pad features a picture of a skull on the wall in the living room…
...and so does the Victorian era version of the residence – at first glance, at least.
Look a little closer and you'll see that the skull on the wall is actually a woman staring into a mirror. Spooky.
The writing on the wall
Blink and you'll miss the initials VR on the wall in Sherlock's living room. They've been blasted in by bullets, which the sleuth likes to fire when he's bored or angry.
Holmes loved shooting the names of the most famous folk of the day into his wallpaper and this time around they stand for Victoria Regina, aka the monarch of the day.
The Persian slipper
Did you spot Sherlock's rather fancy tobacco dish?
It pops up in the modern day 221b too.
The deer with the ear trumpet
In modern day Sherlock the deer skull on the wall sports a fetching pair of headphones, so the show runners decided to pay tribute to them by giving the Victorian deer its very own ear trumpet.
And finally, the secrets in the stained glass
We've previously commented about the patterns and pictures on Sherlock's stained glass door but finally our suspicions have been confirmed by Mr Moffat.
That pane of glass we spy features The Hound of The Baskervilles (the creature on the blue background, Five Orange Pips (those yellowish orbs), the lion from The Lion’s Mane (you'll find four of them), The Mazaran Stone, and the snake from The Speckled Band.