Other mistake: Several times in the game such as talking to the socialite who was burglarized in the Vice case "Naked City" the characters are said to have brown eyes yet they have blue eyes.
Continuity mistake: During the Ornstein and Smough boss fight if you kill Smough first you see a cutscene of him falling dead onto his back, Ornstein then places his hand on Smough and absorbs his power. When this happens you can see that Smough has been flipped over onto his front and Ornstein is actually resting his hand on his back - note Smough's armour.