Veteran stunt man Tom Steele replaced James Arness in the fire scene. Steele wore an asbestos suit with a special fiberglass helmet with an oxygen supply underneath. He used a 100% oxygen supply which was highly combustible. It was pure luck he didn't burn his lungs whilst breathing in the mixture.
When producer Howard Hawks attempted to get insurance for the creature, five insurance companies turned him down because "The Thing" was to be frozen in a block of ice, hacked by axes, attacked by dogs, lit on fire, and electrocuted.
When Scotty mentions having attended the 1928 execution of Ruth Snyder and Judd Grey, another character asks him if he was able to get a picture of it. Scotty answers, "No, they didn't allow cameras, but one guy - " He is interrupted by the Thing's approach before he can finish the sentence. Scotty is referring to Chicago Tribune photographer Tom Howard, who smuggled a miniature camera into the execution chamber strapped to his ankle and was able to take a famous photograph of Snyder's final moments in the electric chair.