Glass?
What's with Billy and Glass? I know glass was the \"character\" in Machina, but what about in songs like Zero? \"I'm the face in your dreams of Glass\". Just a random thought.

A glass fetish? sorry bad joke. Anyways, I don't really know, we could overanalyze and try to say it something to do with glass being a reflective surface and mirrors being a reflection of you-\"my reflection, dirty mirror, has no connection, to myself\". For some reason the line in Ruby, where he says, \"Breathing underwater, and living under glass\", seems to evoke memories of Catcher in the Rye (definitely NOT my favorite book, but I digress). Because Holden wished he could hold every one in glass containers (or something like that), as to hold them at a moment in a time, that they never would change. Glass' Theme with \"shattering glass\" repeated is fairly obvious, the metaphor of someone falling apart and fragile, and all that. But yeah I don't really know why. He probably just thought it sounded cool at the time. Then when it came to creating the Machina Mystery, he noticed some coincidences or inclinations in his songwriting to use certain words tons of times, and made them characters or elements in the story, ex post facto.

I don't think it's necessarily overanalyzing. Glass, in context, always has a deeper meaning that makes it suitable for what he's trying to convey at the time. It makes perfect sense in Zero (both as glass itself and with regards to mirrors), and continues to make sense as the concept of glass evolves throughout the ages. It culminated in the Machina character which was the sum of the previous references. You could say that it was used simply to make the previous references fit, or simply randomly built off of them, but I think the same things that drew him to glass metaphors throughout his songwriting drew him to using glass as a character. The idea of glass being beautiful, but fragile and breakable... and generally an empty vessel which can be filled with something's reflection... those were all appealing concepts that would manifest in Glass.