Continuity mistake: In the film's final scenes at the fuel storage facility, full sunlight is streaming through the overhead rafters. Moments later, it's completely dark and the plant's floodlights are all turned on. A few shots further on, the lights are off and it's daylight again.
Continuity mistake: As John Wayne leaves the landing craft he loads a stripper clip into his bolt action 1903 Springfield rifle. A minute later his rifle has changed into an M-1 Garand.
Continuity mistake: In the very last minute of the film, Cheetah (the chimp) drinks some water that was from the fountain of youth and instantly changes into a baby chimp. But the baby chimp is a different species - a monkey with a long tail - and appears fully grown for that type of monkey.