 The scene wherein the Doctor talks to Sally via a DVD extra was created by writing a conversation, removing Sally's lines, then having David Tennant record his lines.Moffat felt that this one-way filming made the performance more convincing.Moffat initially wrote placeholder dialogue in the script for the scene where the Doctor tells Sally that he can hear her in the DVD shop, because he knew the lines that appeared would have to play "double duty later on" and be authentic and fresh both times.