'Soundbite Animation':

The third animation was where things started to get more complicated for me, when working with animating the mouth and body movements of these two characters (especially 'Young Actor'). 

In this scene, YA responds to OA's previous nonsensical line-reading with his own (equally-nonsensical) reading. This causes OA to shout, stop mid-sentence, then proclaim it's his own turn (to act 'properly').

A lot more motion was developed during the making of this scene, especially with the lip-syncing, which was taking up a large portion of my time.

(Below) Screenshots from the finished scene.