Again, under the cut are doctor who spoilers...kind of...if you care
So in his extended interview Mr. Smith (HA! That's gonna be funny if he...as the doctor...introduces himself as that in the show at any point)...is very grown up and I think he could come across as wiser than his actual years (which is great since he's only a month older than I am....Ooooo now we can say Jesse is older than Dr. Who).
Also I think once you see him in video you can see how animated his face is and he has certain characteristics about his face that remind me of various versions of the doctor. Wrinkly forehead, deepset eyes...and then there's the crazy hair.
My only suggestion...please give him real eyebrows.
Doctor Who Confidential: Interview With Matt Smith