In the first of them, I mentioned that one of the reason I liked her is that I found her charming for being, among other things, so self-effacing. This will give you some idea.
It's from an appearance on the David Letterman Show, where she's promoting the movie, Pitch Perfect. We hear her refer to her geeky ways, and it becomes clear from Dave's response that this has been a common theme through the interview, describing herself as a geek and dork and such. And then, he asks her to re-create a wonderful, musical moment from the movie.
It's a terrific little performance, and clearly prepared. But it's still geeky. And on shows like this, actors like to portray themselves as cool and special and Stars. To do something geeky, that risks failure on live TV -- no matter how good it is (and it's wonderful), that's something most actors don't want to do. (And from experience having worked on many movies, something most attractive actresses don't want to do, wanting to maintain that aura and spot on the pedestal. I'm not saying that pejoratively, just describing a reality, and perhaps even somewhat understandable reality, of movie promotion.)
Anna Kendrick has no such qualms.
(A word of warning. The video stops for a couple seconds, asking you to "Click here" if you want to see something else. I'm guessing you won't want to -- so just wait a brief moment and it will continue on.)