Fringe: Season 1: Episode 20: “There is More Than One of Everything”

Peter on a trip to the past.
Season one finishes off with a trans-dimensional bang, and quite the cliffhanger. This episode was refreshingly easy to watch.
This episode is debunked at Popular Mechanics and Polite Dissent, and you can read more about it at Fox, IMDb and the A.V. Club.
Random thoughts
Mr. Jones shot Nina at point-blank range – surely he could have killed her if he’d really wanted to. Perhaps he just reckoned without the Kevlar-coated ribs (which would probably not have worked exactly Wolverine-style as several layers are needed for decent bullet resistance).
Wait, Nina’s “priority one grid search” on Walter couldn’t have been used to spot a highly-conspicuous guy in sunglasses and bandages?
There are shades upon shades of Philip Pullman’s His Dark Materials trilogy here, with references to alternate worlds, weak points between them, children as a resource and the opening and closing of crossings.
So the fundamental constants aren’t as fundamental as we think? A gradual decay would have appalling repercussions, and this is a particularly unsatisfying explanation for the “weak” points between realities.
And, of course, there are no known parallel dimensions – though it’s nice to see this sci-fi staple getting another airing.