Continuity mistake: When Shirley Maclaine goes swimming in the blue lagoon, her hair is all wet before she enters the cave, but once in the cave her hair is only wet on the ends.
Visible crew/equipment: The shadow of a camera and cameraman are revealed on the left side while the President (Frederic March) is moving from one room to another (door jamb), after learning about Martin Balsam's death. (01:20:00 - 01:21:00)
Factual error: At the start of the excommunication scene, the monks are chanting Dies Irae, a thirteenth century Catholic poem, but St. Thomas Becket died in 1170, almost a century before the poem was written.
Continuity mistake: When Daffy is clawed by the bear, he loses his hat in the process. But when we Daffy running in the next shot, the hat is back on his head again.
Continuity mistake: When Bruno goes to the Captain, to ask for leave so he can go to his daughter's funeral, he places his cap on the desk in front of him. It slips to the floor, but a minute later his cap is magically back on the desk.
Continuity mistake: When we see a close-up of the meter, there is a box saying "10 Centavos for One Hour." The words were not in the box in the previous shot.
Audio problem: When the Big Bad Wolf is blasted through the wall a second time, we cut back to Bugs who says "I don't see why anybody thinks these club initiations are dangerous." When he says it, the audio is a few frames behind his mouth.
Other mistake: There were no gorgons named Megara. The three that existed were Medusa, Euryale, and Stheno.
Factual error: The radio Walter uses on the island has no apparent power source; we never see either batteries or a hand-cranked generator.
Factual error: In reality, Commodus did not die in the arena - he was strangled in his apartments in 192 A.D. by an athlete who was hired by a group of Senators conspiring against him.