When I was an undergraduate some thirteen years ago, we watched an educational video in a "practical" physiology class. The reason it was a video was for animal welfare purposes: by recycling a video made in the seventies, various instructional things could be demonstrated without the need to unnecessarily dissect other critters. Anyway, in this video a much younger version of one of our lecturers took the fluffiest whitest bunny rabbit I had ever seen, anaesthetised it, shaved it, hooked it up to various life-support systems, and opened it up to demonstrate the workings of the contents.
At one point in the proceedings (I think it was at the point the lungs were removed) I had a sudden horrible realisation and turned to my neighbour and said "They're not going to be able to put the bunny back together again, are they?" Until then, I'd been kind of assuming that at the end of the demonstration, everything would be popped back inside the rabbit who would be stitched back together and given a carrot.
Anyway, the concept of not being able to get the bits back in the metaphorical bunny is something I frequently use when describing films. For instance, in The Departed, there comes a moment when you realise that there is no way out for certain characters, and a happy ending is impossible. So next time I'm watching a film and say "I don't think it's going to end well for the bunny", that's what I mean.