EXTRA:
Here you'll find trivial information about the film.
When Joel goes to the darkened room of the recording session in his head for the second time, the warped faces of Dr. Mierzwiak and Joel are (according to Michel Gondry) the skin of his knee.
When Clementine and Joel are in the Montauk beach house, Clementine finds an envelope that says David and Ruth Laskin. David and Ruth are the first names of Kate Winslet and Jim Carrey's assistants.
Unnoticed visual effects that were not planned while shooting were used in the movie. In one shot, Clementine is walking on the street while a car falls in the background. The whole background was replaced with a CG-background, including Clementine's other leg which disappeared, so the remaining leg was done with CGI. Another shot done in CGI was the house Clementine and Joel were breaking into, which collapses in a four-second shot.
The original screenplay by Charlie Kaufman included a short conversation between Joel (Jim Carrey) and Clementine (Kate Winslet) about the album "Rain Dogs" by Tom Waits during one of the opening scenes on the train. During this conversation Joel says he remembers buying the album and liking it, but he can't remember anything about it. While the dialogue was stripped from the film, during the fast shots of Stan (Mark Ruffalo) showing Joel the items he has brought in that remind him of Clementine a copy of the CD "Rain Dogs" can be seen for just a moment. Also the "blue ruin" reference comes from a lyric on the same album.
The 'real' Clementine, that is to say not a memory or figment of Joel's imagination, is only in the film for roughly 20 minutes (and is instantly recognizable by her blue hair).
The original script featured a cut beginning and ending sequence that took place in the future. In the end, an older Clementine comes in to have the procedure done and a look at her screen shows that she's had the procedure done multiple times and all of them involved Joel. At the very end of the script, an older Joel calls Clementine to ask why she hasn't called, but the technicians performing the procedure erase his message. Other cuts in the original script include a montage of memories people wanted erased, including a soldier seeing his dead friend on a battlefield and a girl who was raped at a young age. Another sub-plot dropped from the script was Mary (Kirsten Dunst) finding out that Howard (Tom Wilkinson) made her get an abortion after they had the affair resulting in her desire to have her memory wiped.