Martin Freeman has had a long and varied career, first appearing in the original - and admittedly far superior - UK version of the sitcom The Office, and then as Arthur Dent in the big-budget movie remake of The Hitchhiker's Guide to the Galaxy. He's also known for his portrayal of Sherlock's put-upon assistant John Watson in the BBC's modern reinvention of Arthur Conan Doyle's classic adventures (created by Doctor Who's showrunner Steven Moffat, no less - so he's definitely in the right crowd there!), and, of course, Bilbo Baggins in Peter Jackson's epic Hobbit trilogy. As you can see from his sparkling résumé alone, he already has extensive experience of the sci-fi/fantasy realms as well as with comedic roles, which makes him an ideal candidate for Doctor Who which is known for encapsulating the best of all of these genres - and then some. As an actor, he possesses the kind of effortlessly low-key charm that would serve as an interesting contrast to the tightly wound personality of the Twelfth Doctor. It's easy to see him as a Harry Sullivan type. Someone quintessentially British and extremely proper - someone very likely to be skewered by Capaldi. It probably wouldn't be a very long relationship as a result, but it would certainly be fun to watch while it lasted.