He just does such great childlike delight.
He does. And it's a mystery to me how he does it, because when I was screencapping the pilot, I got all disgruntled, because it felt to me, looking at the stills, that Jarod only had three expressions: happy, sad, and stern. And yet the strength of the acting is how he can jump from childlike delight to utter coldness and back again. 'Tis a puzzlement.