Given a Cinderella story in which Cinderella is represented by Tedd Verres, I couldn't NOT comment on this.
Nonetheless, I am sorry.
TO CLARIFY! In French, as the comic says, Verre and Vair sound the same. The version of Cinderella this is most inspired by was originally French, the title being Cendrillon ou la Petite Pantoufle de verre. The author, Charles Perrault, introduced several elements to Cinderella that are well known today, but as previously commented on, he did not invent the whole story.
It's therefore possible that the elements he's credited as introducing were already part of renditions of Cinderella he'd heard told by other people, including the "verre" part.
It is my understanding that, long ago, someone made the claim that "verre" was SUPPOSED to be "vair", and verre, glass, was used in error.
My understanding is ALSO that there's no solid evidence to confirm this claim, but that it has its own sort of popularity nonetheless, and that some people will claim Cinderella was actually supposed to be wearing vair slippers.
For what it's worth, I believe Perrault intended verre, and they are supposed to be glass slippers in his version of the story. As many versions of the story exist, however, with tons of people borrowing from tons of other people and changing whatever they like, there definitely could have been versions of the story being told with vair slippers.
Personally, I prefer the version that doesn't use squirrel fur.