1. His Child-like Enthusiasm
Watching the Eleventh Doctor, you see that he's not one of the serious, up-tight Doctors. Rather the opposite, this Doctor is quite childish at times, but that's part of his charm. Reminiscent of the Fourth Doctor's goofiness and his sentiment, "There's no point in being grown-up if you can't be childish sometimes," the Eleventh Doctor has the privilege of looking at things and experiencing life both as an adult and through child-like eyes. This is reflective of the show's shift in tone when season 5 started, turning into a more child-friendly show. While some may not like the show's new tone, you can't deny that it certainly fits with the Eleventh Doctor's personality. This is a man that has seen almost everything in the universe and still get excited when he sees a cool-looking toy, a shiny objects, or dinosaurs wandering around a spaceship. Every new thing he sees His childish antics have provided much amusement for both his companions and others who meet him along the way, especially children. When he and Craig are investigating the department store occurrences in Closing Time, he entertains the children with a remote control toy, calling it a better purchase than the boring stuff their parents are going to by. He also set-up a cool room for the Arwell children in the 2011 Christmas special that consisted basically of everything a kid could want aside from actual beds (don't worry, they had hammocks). He also still has a Christmas list and even speaks the language of baby. Put simply, the man is a grown-up child, and it's fun to watch him act that way. I've read a lot on the Internet that a lot of people don't like that he acts childish and occasionally immature. I'm not going to say that Matt Smith's performance is 100% flawless, but each Doctor is a different interpretation of the character. We've gotten stubborn Doctors, empathetic Doctors, guilt-ridden Doctors, swashbuckling Doctors, and multiple others. The fact that Eleven acts childish isn't a bad thing, but rather another way for the Doctor to act. Like I said earlier, Eleven is capable of multiple emotions and personality shifts, so it's not like being childish is his whole character. It's just one aspect of himself, and it's a fun one at that.