2. A Doctor Who Crossover
Now that Matt Smith has hung up his bow tie, we won't ever get to see a crossover between Sherlock and his Doctor - or 'Wholock', as it's known on YouTube. Because of Moffat's involvement in both series, comparisons between Doctor Who and Sherlock are ever-present, as are speculations as to what might happen if their worlds collided. While a five-minute skit for Children in Need would slake the appetite of many a fan, a full-length episode would put the matter to bed forever. https://www.youtube.com/watch?v=q3bGYljQ5Uw Of all the entries on this list, a Doctor Who crossover is the most distant hope. Moffat has said on separate occasions that the two characters inhabit very different universes, and that if they did meet, they would probably would just stand around bickering. On the other hand, Moffat has openly acknowledged the influence that Doyle's stories had on the characterisation of the First Doctor, and even let Smith pose as Sherlock Holmes during The Snowmen. Plus, seeing Benedict Cumberbatch and Peter Capaldi go toe-to-toe really would be something.