When the Doctor first sees himself on the monitor in the castle, there is writing on the stone wall next to the window that is briefly visible in the shot. The lettering is black with red capitals, and it is the opening voice over of this episode ("As you come into this world...") with a few lines missing. See more

Goofs

At the top of the tower where the Doctor places his skull, as he confesses to The Veil there is a close shot of the Doctor with stars behind him and The Veil's hand hovering to one side of his face, you can clearly see the stars in the dark parts of The Veil's hand, showing that they were superimposed over the scene later. See more