Current Doctor Matt Smith
Casting has already begun to find the new 'Doctor Who'.
Although Matt Smith only announced on Saturday (01.06.13) he will be leaving the sci-fi series after this year, the search for the Twelfth Doctor is already underway.
A BBC source told newspaper WalesOnline.co.uk: "The 'Doctor Who' casting call is now underway."
Filling Matt's shoes as the TARDIS travelling Time Lord will not be easy, as his four-year reign as the Doctor has been one of the most popular in the show's history, but early favourites include Chiwetel Ejiofor, Ben Daniels, Russell Tovey, Rupert Grint, Martin Freeman, Ben Whishaw, Colin Morgan, Sean Pertwee and David Morrissey.
Former 'Gavin and Stacey' actor Mat Horne has also registered his interest in taking on the role of the Doctor.
When asked by a follower on Twitter if he is interested in the role, Horne replied: "Of course, but it will not happen."
The 34-year-old star publicly admitted he was interested in the role when Tenth Doctor David Tennant left the series in 2009, but he was beaten to the part by Matt.
Horne previously said: "I'd have loved to do it. I said in the press. The producers obviously had a meeting and went, 'There's this young guy called Matt something who wants to do it. ' And they picked the wrong Matt."
Matt's incarnation of the titular character will come to an end after he appears in the 50th Anniversary episode on November 23 and then the Christmas special.
Tagged in Doctor Who Matt Smith Chiwetel Ejiofor