Revealing mistake: Immediately after Katie is cursed by the necklace, Harry, Ron and Hermione are in Mcgonagall's office talking about what they saw in Hogsmeade. Harry says, "It was Malfoy." As both teachers turn Mcgonagall says,"That is a very serious accusation, Potter." As she says this, she looks oddly transparent. You can see the window pane design through her robes, particularly in the shoulder. This continues to be true until she says "I suggest you go back to your dormitories." This could possibly signify a green or blue screen behind them. (00:54:10 - 00:54:40)
Continuity mistake: When they are at The Three Broomsticks pub Hermione orders 2 butter beers and a ginger wine, but they all drink butter beers.
Suggested correction: Hermoine orders 3 butterbeers and asks for some ginger in hers. She does not order 2 butterbeers, nor does she ask for a separate ginger wine.
Suggested correction: She's not transparent. It's a trick of the camera. A glare from the bright window behind her. You notice you can't see the vertical slats of the windowpane. Only the horizontal. That's because the glare is carrying across her body horizontally and where the horizontal slats are there's no light to cause a glare.
GarlonussI can see the horizontal and vertical ones through both McGonagall and Snape. I can even see the desk through the middle of her body.