5. When I was your age, oh, about a thousand years ago
This is actually a very simple moment, in which the Doctor shows a child what his sonic screwdriver can do. It occurs at a very dark moment in a very dark episode, as the Doctor sits with a scared little boy while one of the terrors of the adult world enacts itself outside the door. The Doctor in this episode is a mediator between the fears of adulthood and of childhood. In this scene, he keeps the fears of adulthood at bay while helping beat back the fears of childhood. The Eleventh Doctor is far more childish than perhaps any Doctor before him, and it shows in his interactions with children. Hes very sweet with them because he feels a lot of kinship with them, but his childlikeness is a choice. Hes an old, old man, and he understands more about people than any child ever could. But, unlike most grown-ups, the Doctor can wave his sonic screwdriver and make magic happen.