The model-makers create the sheep by first moulding their body into shape, then wrapping their bodies in white fleece.
The fleece is then dirtied a little and silicone legs are added. Finally the removable head is put in place ready for their big moment.
"We have a number of bodies, some on all four legs, and some on just two, depending on the scene," says Chris.
"Then the animators make the sheep blink, smile, chew or whatever, using the selection of sheep mouths."