Bingowings said:

I think the boy read the actors well enough, the actors were just acting weirdly (thanks to the director probably).

As I said, the kid didn't get the scene because it is a little more complex. The kid obviously read the actor's expression but failed to comprehend that the main source of the guy's fear was coming from somewhere else (i.e. Emperor).

The entire purpose of the scene was to warm up the audience for meeting the Emperor (to build up his reputation, to preliminary establish his creepiness etc).

I mean I understand that the kid didn't get the scene... but it seems you didn't get it either it. :)