Factual error: Toshiro Mifune's character, Kikuchiyo, travels to the bandits' camp and steals one of their two remaining fuselock muskets. Shortly afterward, the bandits fire twice at the samurai within five seconds with their last firearm. A fuselock takes as much as two minutes to reload, prime, and fire.
Revealing mistake: When O'Keefe takes his bride-to-be Dolaroo to Hong Kong to be married, a 1950's truck goes past in the background. Unfortunately, the film is set in 1870.
Continuity mistake: Caligula orders his chief gladiator to kill a prisoner so he can test the Robe's "powers". The gladiator stabs the prisoner with a dagger and straightens up. Look at the dagger and you'll see no blood on it.
Suggested correction: This may not be a mistake. It's entirely possible to stab either a person or an animal with a quick thrust and retrieve and show very little or no blood. Especially with a slim blade.
Deliberate mistake: After the airplane loses its propeller and descends to lower altitude, the cockpit constantly shakes due to turbulence, and the flight crew complains about it in one scene. However, when the camera switches to the passenger cabin, everything remains perfectly still and serene until the airplane is on its final landing approach near the end of the movie.
Continuity mistake: When Marilyn Monroe tries to untie the raft and Robert Mitchum can just catch the rope it the river flows from left to right. Later, when they take off again together, the river flows from right to left.