Just after Emmy Rossum (Christine) has fainted, the Phantom (Gerard Butler) lovingly picks her up and carries her to bed - this is just after he's shown her the wedding dress. As he carries her away from where the dress is, he takes her up a short flight of stairs. As he carries her up them however, he accidentally sweeps her head through the long curtains that are hung covering the wall. If you watch, you'll see a long curtain cord get caught on her head as he carries her past them, and as he carries her up the stairs blissfully unawares, it pulls free and comes away from her head. Don't know if it was left in on purpose or not, but it makes me giggle every time, to see the Phantom lovingly sweeping Christines head through the curtains.