Blending Two Shots for Continuity
Very easy to do, well theoretically.  On cut actor freezes his body, friends places the prop - in this instance the cat, on action the actor continues his movement.  The quicker and non intrusive the introduction of the prop, the less movement the actor will have and the more seamless the cut will look.

The main thing to remember here is to be prepared to have a lot of takes.. it will take time to get it right.