Fred Zinnemann and producer, Samuel Marx, invited Morton Thompson, the author of the underlying material in his book 'Joe, the Wounded Tennis Player,' to a Projection Room screening of the first rough cut, which included 'Scene Missing" tags and ragged sound. When that first screening ended, Mort got up, never looked at either Zinnemann or Marx, and walked angrily out, slamming the door. Marx commented that obviously, authors do not need their written word to show their unhappiness.
The horse named The Bart was inspired by the actual 1919 Preakness (and Triple Crown) winner Sir Barton.