Charlie's leaking ear infection changes sides and mysteriously spreads from his right ear to his left after he returns from one of his enigmatic trips.
In one of the final shots of Colonel Lipnick in uniform, the bottom two rows of his ribbons have come lose and are hanging from one side. In the last shot, his ribbons have been fixed.
After Barton tacks up the first strip of wallpaper, he smoothes out the second strip and, in close-up, we see that the first thumbtack is not there.
When Mundt pulls the bedframe apart, the metal ball that drops to the floor has a metal rod through the center. When it hits the floor, the rod is nowhere to be seen.
When Barton meets Charlie for the first time, the fan behind him on the desk changes speeds. The strips attached to the fan are first slack, then blowing out, then slack again.
As a civilian, Barton Fink would not have been allowed into a USO dance.
Colonel Lipnick's uniform contains awards created after 1941, including a Master Parachutist Badge (1949) and the Combat Infantryman's Badge (1943).
Approximately 22 minutes into the movie a red light flashes on Barton's chest below his left ear just after he finishes the line, "And what's your line, Mr. Meadows?"
Briefly visible at the top of the screen when Detective Mastrionotti introduces himself to Barton.