The episode incorporates the song "Wonderful! Wonderful!" by musician Johnny Mathis. Having read the screenplay Mathis refused to allow his version to be used, owing to the episode's graphic content, and a cover version had to be created. Producer David Nutter, who had a background as a singer, intended to record the vocals but at the last minute another singer who sounded more like Mathis was hired. Manners explained that he wanted to use the song because "certain songs 'Wonderful! Wonderful!' have a creepy, icky quality that none of us have really openly acknowledged".