The popular TV double act posted a picture of themselves mucking around as they started work on the highly-anticipated next three episodes of the BBC One drama.
The BBC One Twitter account teased: "Sherlock read-through over, plenty of surprises in store for series three!"
Martin Freeman confirmed on Graham Norton's Comic Relief Big Chat last week that series three of Sherlock begins filming later this month.
Freeman described the scripts as "brilliant", but insisted that he still didn't know how Sherlock Holmes had survived the cliffhanger ending of the 'Reichenbach Fall' episode.
"Even we on reading the script aren't quite sure [what happened]," he said. "[Writer] Mark Gatiss is a clever fella."
At last year's Edinburgh TV Festival, Sherlock creators Steven Moffat and Mark Gatiss revealed the teaser clues 'Rat', 'Wedding' and 'Bow' as hints for what Sherlock Holmes stories the third series will be based on.
Sherlock series three is expected to air in late 2013.
Watch Martin Freeman discuss the new Sherlock with Digital Spy below: