Just noticed something odd watching a Quicktime movie in Safari. If, at any time while running the movie or after it's stopped, you hit cmd+BackArrow, instead of going back to the previous page as usual, the clip plays in reverse. In order to go back you've actually got to mouse over and hit the back button, which then works normally.
Although this seems like a bug, I've been having just the most fun with it playing things backwards. Check this out to get started. Let it load all the way through without watching it. Put the cursor at the end, hit cmd+BackArrow, and enjoy.