The extra scene at the end with Ewan McGregor and Renée Zellweger singing a duet was filmed at the insistence of Zellweger and McGregor. They said that with both of them having been in musicals previously (McGregor in Moulin Rouge! (2001) and Zellweger in Chicago (2002)) that it would be a sin not to.
To create this movie's vivid, stylized appearance, cinematographer Jeff Cronenweth digitally color-timed the movie to simulate the appearance of three-strip Technicolor.
Everything the characters wore, literally from head to feet, was custom-made for them.
The split-screen telephone calls scenes are direct homages to 1950s and 1960s screwball comedies, Pillow Talk (1959), in particular.
During the dating montage, one of the scenes in the background is of a man playing bongo drums. This footage was taken from the scene in Pillow Talk (1959) when Doris Day's and Rock Hudson's characters first meet.