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.
Stan and Mary dancing over the unconscious Joel in their underwear was improvised.
The voice whispering "Mantauk" is a combination of Kate Winslet's voice and an editor working at Focus Features. The woman was asked to do a quick voice over before Kate Winslet arrived, and they left it in.
Viral Marketing: A website for Lacuna Inc. was created to promote the film. It contained a link to watch Joel experience the procedure, which would link to the movie's official website.
What Could Have Been: Besides Mary's deleted subplot and the additional ending mentioned below, there was to be a montage of people who wanted their memories erased - a soldier seeing his dead friend on the battlefield and a girl who had been raped at a young age.