The actor-turned-director and film pioneer admits he called on the puppeteers from the hit Broadway show to help him create the character Boxer in his new movie - and the results were initially striking.
He tells The Hollywood Reporter, "We literally took the horse puppet and put markers on it. The performance looked extraordinary, but then we looked at the digitised version, and we noticed that the spine wasn't working as well as it was to the naked eye.
"We had to rethink it and realised it needed a flexible spine. We actually took the puppeteers out of inside the puppet and attached a flexible spine - and it works rather well. You can see every subtle detail of movement."