10 clever callbacks and Easter eggs in Sherlock you probably missed

You might have binge-watched Sherlock a million times but still missed some of the clever callbacks and Easter eggs in the show. That’s because only Sherlock Holmes has the keen sense to spot the minutest of details, and sadly, none of us is him. Also, the show does such a great job at hiding these Easter eggs that it’s impossible to catch them if you aren’t paying attention.

Sherlock is a treasure of callbacks, like codes from Victorian tales and sly props. Fans of the show are so engulfed in the grand mysteries and mind-boggling scenes that many must have missed the sly nod to the original stories by Sir Arthur Conan Doyle. They might have also overlooked the hidden Doctor Who reference in the background.

So, light a pipe, put on your hat and overcoat, and check out all the hidden Easter eggs and callbacks in Sherlock that slipped past your radar.

---

10 clever callbacks and Easter eggs in Sherlock you probably missed

Sherlock is a mystery crime drama series based on the detective novel series by Sir Arthur Conan Doyle. Although the entire series is rooted in mystery and thrill, viewers expect to be surprised frequently, but the show has found creative ways of doing it.

Instead of just surprising the viewers with its stories, Sherlock includes many Easter eggs and callbacks that pay homage to the original books. Here are 10 such hidden gems that even the most eagle-eyed fan must have missed.

10) Yellow smiley face on the wall

For those who don’t know, the yellow smiley face on the wall is painted in Sherlock’s flat. It is a nod to the original stories where Holmes would shoot bullet holes into the walls and spell out “VR” (Victoria Regina) while feeling bored or uninspired. The smiley face seemed like a better alternative to the bullet holes. Normally, people would meditate or seek company during such times, but Detective Holmes is anything but normal.

---

9) A Scandal in Bohemia/Belgravia

One thing the Sherlock TV series is known for is sticking to its roots. The writers adapted the original stories of Sir Arthur Conan Doyle and gave them a modern twist. The best part is that these adaptations include sly callbacks from the original stories.

In the short story A Scandal in Bohemia, Sherlock disguises himself as a priest to obtain incriminating photos from Irene Adler. In the BBC series, this story was adapted as A Scandal in Belgravia in Season 2, Episode 1. It turns out that this priest costume is Holmes’ favorite — and it’s taken directly from the story.

---

8) Seven per cent solution

Hound of the Baskervilles is one of the most recognizable Sherlock Holmes stories, regarded as one of the most famous mysteries ever written. In the book, Holmes and Watson solve the case behind the mysterious death of Sir Charles Baskerville, which is linked to an old family curse involving a demonic hound. Eventually, the duo discovers the curse is a cover for murder.

In the books, Holmes is addicted to a seven-percent solution of cocaine, which he uses to stimulate his mind while solving mundane cases. In The Hounds of Baskerville (Season 2, Episode 2), Mrs. Hudson offers Holmes tea, but he retorts that he needs something stronger. He then mutters “seven percent stronger” under his breath.

---

7) Watson's blog headlines

In the Sherlock TV series, all the cases John mentions in his blog are similar to Sir Doyle’s original short stories. But since the series is set in modern times, the headlines are century-appropriate. For example, The Greek Interpreter became The Geek Interpreter, The Speckled Band became The Speckled Blonde, and The Naval Treaty became The Navel Treatment.

---

6) John Watson or James Watson

In Season 3, Episode 1 (The Empty Hearse), Sherlock returns to London and reunites with Watson to help Mycroft uncover a terrorist attack. The episode was inspired by two original stories: The Adventure of the Empty House and The Lost Special. It was also the episode that introduced Mary Morstan.

Here, Mary receives jumbled, anonymous text messages, which she recognizes as skip code. One of the messages reads “John or James Watson?” This is a nod to The Man With the Twisted Lip, another short story by Sir Doyle, where Mary refers to Watson as James instead of John. This incident even made fans theorize that Dr. Watson’s middle name is Hamish.

---

5) Vatican Cameos

“Vatican Cameos” is a phrase Sherlock and John use as a kind of code word for immediate danger. It is mentioned two more times in A Scandal in Belgravia and The Sign of Three. In The Hound of the Baskervilles, Holmes also refers to being “exceedingly preoccupied by that little affair of the Vatican Cameos.”

Watson uses the code to warn Holmes over their comm devices about Sherrinford’s governor being compromised. The term “Vatican Cameos” is actually lifted straight from Doyle’s writings — a mystery that Doyle never expanded upon but left as an intriguing throwaway line in the canon. By reusing it in Sherlock, the writers turn a small footnote from Doyle’s world into a dramatic inside joke — a wink to readers who know the reference. That makes it a textbook Easter egg.

---

4) Shoes & Tobaccos

In the original stories, Sherlock has a habit of storing pipe tobacco in a Parisian slipper. This cheeky detail was cool enough to be included in the series, and the writers found the perfect moment for it, too.

As everyone knows, weddings can be a stressful event, especially for the groom’s best friend. So, during Watson’s wedding, Holmes manages to stuff cigarettes into his slippers.

---

3) Toby the dog

In Doyle’s The Sign of Four, Toby was Sherlock’s loyal tracking dog, celebrated for his sharp nose and reliability. Sherlock brings back Toby, but with a twist: here, he’s not particularly helpful and often seems more of a hindrance than a solution.

This contrast is deliberate. Benedict's Toby wasn’t as helpful, but he was still a clever callback. The show didn’t just borrow the name; it reintroduced a classic character and then subverted expectations, turning a trusted ally into comic relief. That makes Toby’s inclusion more than a background detail — it’s a playful Easter egg for fans who remember the original stories.

---

2) Lavinia Smith's book

Throughout the Sherlock TV series, viewers will notice many Doctor Who nods and references. One of them is a book by Lavinia Smith, the aunt of Sarah Jane Smith from Doctor Who. The book can be seen behind Watson in the episode The Lying Detective (Season 4). But be sure not to blink, or you’ll miss it.

---

1) Sherlock's love for Doctor Who

As stated earlier, Sherlock’s love for Doctor Who is seen in many episodes, and there are two reasons for it: Moffat and Gatiss. Steven Moffat and Mark Gatiss are the co-creators of the series, with Moffat also being the head writer and showrunner of Doctor Who. Gatiss wrote several Doctor Who episodes during Moffat’s tenure, besides playing Mycroft Holmes.

Because of their connection to both TV shows, viewers can spot several Doctor Who callbacks and Easter eggs in Sherlock. For example, Holmes’ hospital room had TARDIS roundels on the wall. This is a nod to Toby Jones, who played Culverton Smith in The Lying Detective and the Dream Lord in Doctor Who Season 5, Episode Amy’s Choice.

---

So, there you have it — 10 cheeky and sly callbacks and Easter eggs that went right over your head, just like Moriarty's last line. Every callback complements the show and pays tribute to Sir Arthur’s legacy and Doctor Who. These Easter eggs make Sherlock one of the most layered adaptations ever put on screen.