Factual error: The serum is transported by the blood. Hair has no blood traveling to it, only the root. So unless Bacon shaved his body clean, his hair wouldn't have become invisible, as would all the fur on the gorilla.

Continuity: Why does the Twinkie Kevin Bacon eats disappear immediately? If things that go into him disappear, when they give the needle to the gorilla, you shouldn't see the needle point when it is stuck in her arm.

Continuity: At the end of film when Elizabeth and her lover are escaping from Sebastian in the hall, Liz turned on the fire alarm and everything became wet. But after that they and their clothes are dry.

Continuity: At the beginning of the film a phone conversation tells us that it will be morning soon and Kevin Bacon will meet them at the Lab first thing in the morning. Yet when they show the car driving on the highway to the lab, all of the shadows are straight down.

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 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.

Continuity: When they try to make Kevin visible, they use a blue spray to see his vein (like they did to the gorilla). but you never see the blue mark again...

Continuity: When they're pouring the "goo" on Kevin Bacon to make the mask, some of it gets on the end of his breathing tube. When they change shots, it is clean again.