I am thinking of just getting a stock image of a cat and blocking the animation, to give a better idea of whats going to happen.
There is also an animatic version of the shots. Of course missing Remus again.
Remus walks past and goes off screen behind one of the shelving units. He suddenly does a double take, shooting back with a slight skid. His mouth just drops open with his tounge hanging out.
The camera changes to look at the sandwich on the desk and quickly zooms in on it.
In the distance you see Remus licking his lips and stand up like a Meerkat to get a better view. As its zooming back in on him you see him drop and get into a stalking pose, moving his legs slightly to give the wiggling bum about to pounce move.
There are two mistakes in the video above, one being the zooming back in on Remus being too quick as he couldn't do what I discribed in that time and the second being that the first shot is missing.
WHAT HAPPENS BEFORE THIS SCENE
Before this bit I have added a new bit which is showing who Remus is. He is basically proudly and cooly walking past the fish tanks with either 1.the fish scared and hiding 2.following him in the tanks sticking their tounges out or 3.just winking at him.
He then goes past a snake tank and the snake slowly opens one eye until he notices it's Remus and opens both eyes while lifting his head slowly. Remus grins and nods his head slightly as a greeting and then they hi five each other with their tails (obviously with the tank inbetween). (Remus could lift his back half slightly off the ground during this like some people jump when hi fiving).
He then walks past the shelving units and it is the bit above.
The reason I have added this is because when I asked the guy from Pixar about how I can make the audience like my characters more and feel empathy for them he said that a background story or a brief feeling of what and who the character is, is the best way of doing it and how I do when creating stories for Pixar.
The bit with doing the Hi-5 with the tails was actually from a suggestion from Derek who said to get the tail involved as if its a hand. I saw this idea as being anthropomorphic, give the tail something to do, be comical and different.
Here are some reference images of animals Hi fiving. Obviously no snakes but some cats to get an idea how I could do it.