Factual error: Rats have very poor eyesight but an extremely keen sense of smell. The rat introduced into the gorilla's cage would know right away that there was another animal in the cage and would never scamper happily into danger, as this one does.
Factual error: When they put the gorilla back into the cage in the movie, who is said to be female several times, you can spot that it has a silver back. Female gorillas do not ever have silver backs - it's strictly a male thing.
Factual error: When the crew pour liquid latex over Sebastian's head and neck, in order to create a fairly life-like mask of his face, it simply pours over his head as though he is completely bald, and he is able to remove it later by pulling it off, exactly like a glove. However, the film creators seem to forget that Sebastian has quite a thick head of hair, and technically, when they pour the latex over his head, it should stick and/or pour along the outline of his hair. Whilst drying, the mask should equally have stuck to his hair and become very difficult to remove, and yet as they create the mask, no hair appears to exist on Sebastian's head. They did not shave Sebastian's head - later in the film he falls into a swimming pool and we see a clear outline of his entire body, with a full head of hair. (00:47:15 - 00:48:30)
Factual error: When they inject the serum that counters the invisibility into the gorilla, you see the serum flow backwards toward the gorilla's hand. Veins have special valves that prevent blood flow from going backwards and to force blood to go to the heart, so how the serum manages this is beyond me.
Factual error: When they make the gorilla visible again, her heart becomes audible at the same time it becomes visible. This happens with Kevin Bacon as well. But that shouldn't happen, because it was just invisible, not inaudible. And it wouldn't make a noise like that unless you were listening through a stethoscope.
Factual error: The speed used to administer the serum to Sebastian is not close to the reality. At that speed the vein would have exploded.
Factual error: Duct tape would not stick to bloody skin at 40 below zero, and probably not at higher temperatures either; again because of the blood.
Factual error: The braking system on lifts (elevators) is designed to stop a free-falling car safely and quickly (using gravity and a wedge system). It would not take a long time to stop the car or break up as shown in the film.
Factual error: When we first see Caine (Bacon) enter the military base, there are Willy's Jeeps used by military personnel. By the year 2000, the Willy's Jeep was long-since replaced in the U.S. Military by the HUMVEE, which we also see in the film.
Factual error: You see the serum flow toward the heart and then branch out through the rest of the body. The same thing happens when they try to do it with Kevin Bacon. In ANY normal circulatory system, blood that reaches the heart from the veins has to go straight to the lungs to be deoxygenated before it gets sent to the rest of the blood. The serum clearly doesn't do this - the only way that anything could skip the lungs so blatantly is if there was a hole in the heart.