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.
After Leonardo Da Vinci arrives at the last supper he holds up his right thumb. Then it cuts to a wider shot and he's holding up his left thumb.
When the cave man throws the spear, is penetrates the abdomen of another cave men. When the spear is pulled out, the is no blood on the blade.
When the nuns line up at the side of the pool there are only 12 of them, but then you see 16 of them swimming in formation.
When Nero hands the medallion to his aide and says "wash this," the aide is seen holding the medallion but when the camera angle changes, he doesn't have it.
In the prehistoric man segments, the narrator refers to "Homo sapien" instead of "Homo sapiens".
When Josephus slips on the banana peel, his foot misses the peel.
When Comicus, Miriam, Swiftus and Josephus are escaping in the cart, the shots from behind the cart shows the tire tracks from the vehicle the camera is mounted on.
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.
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.
In the Spanish Inquisition musical number, the nuns do an underwater show that ends with them standing on a menorah. It is clearly visible in the movie that the action is in reverse.
When Comicus performs a Caesar's Palace, he jokes about the Christians. Since the segment ends with the Last Supper, Christianity did not exist yet.
In the segment about the Roman Empire Nero is the emperor, which would set the story during the years 54-68 AD. However when arriving in Judea Jesus is talking about his last supper and the his betrayal, which happened before the year 30/31 AD.
When Comicus is pulled into the Virgin room by Miriam, one of the virgins' says "Who's that?", but her mouth does not match "that".
When the Roman soldiers arrive to present Nero 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.