Visible crew/equipment: When Ethan Hawke is picking out a suit and shoes, you see a distinct hand on the left side of the closet holding up what must be a false wall. (00:33:25)
Continuity mistake: When Ethan Hawke and Uma Thurman are escaping form the party, the sleeve of Ethan's suit is ripped under the armpits when he hits the cop but in a few seconds you see his sleeve completely fixed. (01:11:40)
Revealing mistake: When Jude Law needs to pull himself up the flight of stairs to reach the intercom, you can see him use his hips, despite the fact that he is paralyzed from the waist down.
Factual error: When Vincent and Jerome are at the Gattaca building at night, they watch a rocket launch. The exhaust from a such a rocket would have lit the area around them or at least the nearby mountains bright as day.
Revealing mistake: In the scene where Anton and Vincent are swimming in the ocean, the state of the sea when near the beach doesn't fit with how it is when they're further offshore.
Answer: The leg bones are fractured completely across, at a location between the rings of the device. Thereafter, while the bones are knitting back together, the device is periodically adjusted to drag the bones away from each other a fraction of an inch. The bones continue to grow toward each other to close the gap, gradually lengthening. It is an astoundingly painful way to add height.
Rooster of Doom