The opening sequence features Day singing the Livingston & Evans song, "Que Sera, Sera (Whatever Will Be, Will Be)." The song had been introduced by Day in the 1956 Alfred Hitchcock suspense film "The Man Who Knew Too Much", in which she co-starred with James Stewart. Despite the opening montage of images changing from season to season, Day singing the song off screen during the opening is the one constant over the entire course of the series, with a more family-oriented version (including a children's chorus) in Season 1 and a more adult contemporary version (with a stronger beat) in Seasons 4 and 5.