Ain't Nobody Here But Us Chickens

"Ain't Nobody Here But Us Chickens" was a song playing on the radio when, on 20 January 1941, the Empty Child turned it on which his psychic powers. The Ninth Doctor soon afterwards told the child, "Nobody here but us chickens", soon correcting himself when he noticed the song had stopped playing — "this chicken". (TV: The Empty Child)

Behind the scenes
This is yet another of the differences between the real world and the DWU: in the real world, "Ain't Nobody Here But Us Chickens" was released in 1946, five years after the events of this story.