 At the start of the film when the Brothers Grimm are talking to the  queen about the many different versions of the Cinderella story they  mention that in some versions the slippers she wears to the ball are  fur rather than glass. This refers to Charles Perraults version of  the story, which was the first to introduce the glass slipper (which  in French is "pantoufle de verre"), and how some people believe it  was actually an misinterpretation of the words for a fur slipper  (pantoufle de vair).