Revealing mistake: When Lucy is chained and locked up in the room by the Korean drug cartel, she is hit in the stomach by the Korean guy. Drugs start leaking into her stomach and her body, and she starts shaking and going up the wall and ceiling. When she is leaning against the wall and crawling up it, the way the gravity affects the chains and her hair shows that she is actually lying on the floor. (00:25:20)
Revealing mistake: After the drug addict gets shot, one of the henchmen lifts the dead drug addict's leg up and the other leg lifts up with it before the second henchman had a chance to grab it. It looks unrealistic as if it is a prop rather than a real human being dragged.
Revealing mistake: In the scene where Lucy causes the bullets to fall out of a loaded pistol the casings that hit the floor have a firing pin mark in the primer with the bullet in the casing.