I thought it was a detached ending that seemed thrown together quickly as if at the last minute. It seems a show of the King of Queens' caliber should've ended on a more enlightening note - perhaps a marriage or an entertaining song and dance number. The way we left Doug, Carrie, and Arthur seems quite disturbing and unenlightening.
Also, "that song" was Milk and Honey by million/billion.
Also, "that song" was Milk and Honey by million/billion.