The scene where Joel and Clementine watch the circus go through the streets was made up on the spot, as the film crew and cast happened to be working nearby and Michel Gondry decided it could work well in the film. The part where Clementine disappears suddenly is one of Gondry’s favorite moments of the film, as Jim Carrey didn’t know Kate Winslet was going to disappear and Gondry likes it because Carrey’s face appears so saddened. When the sound blanks out in the final film, Carrey is actually saying “Kate?”

Virtually all of the most bizarre and fascinating scenes in this movie were created with old fashioned camera, editing, lighting and prop/set tricks. The use of digital effects was very limited. The striking kitchen scene with Joel as a child was created with an elaborate forced perspective set-up similar to some used by Peter Jackson in the Lord of the Rings trilogy.

When Joel is in his head and is visiting his session of the erasing process, no special effects were used to show the two Joels in the one scene. Jim Carrey had to take off his hat and jacket when he was not in shot and had to quickly sit down in the chair and visa-versa when he has to stand up.

The audio for the scene in which Joel and Clementine appear as children in Joel’s memory while their adult voices converse was recorded on location, rather than dubbed later in a studio. Director Michel Gondry felt it was better to have Jim Carrey and Kate Winslet reacting to the children playing their characters as it happened.

Despite the fact that Charlie Kaufman’s script and Michel Gondry’s visual concepts were closely followed, the actors were allowed many chances to improvise. Elijah Wood and Mark Ruffalo improvised extensively, and much of the dialog between Jim Carrey and Kate Winslet resulted from videotaped rehearsal sessions during which the two actors became close by sharing tales of their real life relationships and heartbreaks.