There have been 13 incarnations of the title character in the BBC series Doctor Who since 1963. Although it may be hard for fans to imagine any other actors playing those parts from the past, they do have to get used to someone new in the role every few years. An even more jarring shift would be to see the Doctor as an American. The Tumblr blogger Smug Mode came up with some interesting casting of American actors in each of the Doctor Who eras. Do you agree with the selections? See them all, in order at Geeks Are Sexy.