The main cast of BBC’s Elementary, and the BBC’s Sherlock.

Created by Mark Gatiss and Steven Moffat, Sherlock is a modern version of the famous detective, his cases, and all those around him. The series stars Benedict Cumberbatch as Sherlock and Martin Freeman as John Watson, who come across with some notable characters from Conan Doyle’s stories, such as Jim Moriarty (Andrew Scott) and Irene Adler (Lara Pulver), with modern-day London as main setting. The first episodes were very well received, making way for three more seasons and one special episode, and one of the most praised elements were the performances of Cumberbatch and Freeman.

Related: Sherlock's Original Pilot Explained (& Why It Was Changed)

Cumberbatch and Freeman’s versions of Sherlock and Watson were very popular among fans of the source material, but Sherlock could have had a very different John Watson, one that ended up playing another iconic character, also produced by Moffat.

Sherlock: Matt Smith Auditioned To Play John Watson

Matt Smith is The Doctor

In 2010, Sherlock Holmes either as Cumberbatch was already cast, so he was out. At the time, Smith had only starred in TV films and a couple of TV shows, as well as two films, and was mostly known for his stage work.

That failed Sherlock audition wasn’t a waste of time at all, as it helped Smith get the role of the Eleventh Doctor in The Hobbit trilogy and is now part of the MCU, where he plays Everett Ross. John Watson wasn’t a role made for Matt Smith, but that experience ended up opening more doors for him.

Next: Sherlock's Biggest Mistake Was Bringing Holmes Back From The Dead