Factual error: The serum is transported by 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 wouldn't all of the fur on the gorilla.
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Mistakes
When Isabelle (the gorilla)'s body hair is returning, you can see Linda (Elizabeth Shue) touching it. In that shot, the leather belt above Isabelle's body actually seems to be hovering above her - it is not resting on her. See more...
Hollow Man (2000)
Directed by Paul Verhoeven, starring Elisabeth Shue, Josh Brolin, Kevin Bacon, Rhona Mitra (add more)
Hollow Man mistakes
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.
Hollow Man trivia
When Sebastian gets frustrated with himself in the lab, he stands up, walks, turns and beats his fist twice on the table. This is the same thing Kevin Bacon does in Footloose to his VW Beetle when he gets frustrated with the town.