Filmed in April 2005. The writers were still working on the script when filming began. As a result, the ending narration was written based on the visuals that had been filmed.
The episode title, "One Wonderful Day", is taken from a song of the same name in the Stephen Sondheim musical, 'Saturday Night' (1955).
The episode drew over 30 million viewers upon its initial broadcasting in the United States, becoming the most-watched program of the night across all networks. It was also the most-watched season finale for a freshman series, since ER ten years earlier.
ABC accidentally leaked on their website a photo of a scene, that was cut out of the season finale. The photo revealed the Applewhites's big secret. The network had the photo immediately pulled.