I did an experiment in iMovie and made a backward copy of FWWM. I wanted to watch it that way to see if I could understand any of the backward talking more easily — I couldn't. What was interesting though, was that some of the music sounded the same as being played frontward.
If there is enough interest, I'll upload the backward version to Vimeo or DropBox.
I've watched the documentary called Room 237 many times (about Kubrick's The Shining), and one of the spots in it was a fan who double exposed that film to play backward and frontward at the same time, with amazing results. So, that'll be my next test to see how that looks.
The "backwards" talking was done by the actors speaking words backwards phonetically, for example "let's rock" is "kar stell" and then running the footage backwards. Movements also had to be done in reverse.