Well, I think the ur-example of breaking the glass is Angel in the X3 movie -- the moment where he takes the binding off of his wings, refuses to take the drug that would make him normal, and goes crash! out flying. I don't know if I can come up with enough examples to think about the statistical likelihood of transformative narratives, though!

I think the watching-the-reunion through glass is also a great example of the moment of longing and isolation! And so is the tv screen, which I also hadn't thought of -- there are examples of people separated by the TV screen and death in Buffy, too. (Oh, Faith!)

The wall and the tv screen and all of that is a demonstration that scifi's pretty good at this sort of metaphor, really!