Joining the franchise in 2010 at the Eleventh Doctor, Smith was the youngest actor to ever portray the character. (He was just 26 at the time.) As such, producers had fun contrasting the character's world-weariness against the actor's youthful appearance. There was an energy and a playfulness to Smith's approach to the character, which, in some ways, made him not all that dissimilar from his predecessor. Not that that's a bad thing--his adventures with Amy Pond (Karen Gillan), Rory (Arthur Darvill) and River Song (Alex Kingston) over the course of his three seasons are some of our all-time faves--but if we're splitting hairs (and we totally are), the other guy did it first.