When the Roman soldiers arrive to present Cesar with the spoils of war, a fanfare sounds. However when the shot cuts to the soldiers entering, the heralds (trumpeters) are just starting to bring their horns up to play them.
In the beginning of the Roman Empire Segment, one of the running jokes was the use of a V in place of a U. It seems that great care was taken to do this on every sign. Except the Annual Orgy sign which has two Us on it that were not changed to Vs. U's are also visible on the "Equal Opportunity Employer" sign at the Unemployment Office.
During the Stone Age segment, when Orson Welles narrates about the Cavemen discovering "Humor", A caveman unsuccessfully tries to humor the others with his comic routine before being snatched away by a dinosaur. As the dinosaur snatches the caveman comedian away, you can see the cables used to hoist him.
When Comicus and the others are escaping from Rome in a carriage being pulled by Miracle, the carriage has thin narrow wheels, however the tire tracks it leaves when they're pulling away are wide and have treads like regular car tires.
When Comicus, Miriam, Swiftus and Josephus reach the 'river', the tops of the water remover are obviously visible just below the surface. Later, it is obvious that the water is being dumped into a pool-like area in the middle of the river to create their path.