Throw It In: A scene length one. While filming in downtown Manhattan, they heard that there was a circus parade going on outside. Gondry grabbed a portable camera, and got some footage of Carrey and Winslet messing around in the crowd completely anonymous due to it being night time and since the actors were wearing winter gear. The result is one of the happier memories in the movie.
Word of God: In an alternative script there's an extra ending, where an older Clem goes back to Lacuna to erase Joel again, and an older Mary reveals to her that Clem and Joel have been erasing and re-erasing each other for years, always ending up back together.