Date: 5,000,000,053
Location: New New York, New Earth, Galaxy M87

This episode marks the first appearance of the Macra since their debut in the 1967 serial "The Macra Terror".

The description that the Doctor gives of Gallifrey is identical to the one given by his granddaughter Susan in the 1964 serial "The Sensorites".

The Face of Boe tells the Doctor that "everything has its time." This echoes the Doctor's words in the 2005 episode "The End of the World".

The Doctor: (describing Gallifrey) It's quite like Earth but at night the sky is a burnt orange and the leaves on the trees are bright silver.

The Face of Boe: (to the Doctor) Everything has its time. You know that, better than most.

The Face of Boe: (his final words) But know this, Time Lord: you are not alone.

The Doctor: There was a war. A Time War. The Last Great Time War. My people fought a race called the Daleks for the sake of all creation. And they lost. We lost. Everyone lost. They're all gone now. My family. My friend. Even that sky. Oh, you should have seen it, that old planet... he second sun would rise in the south, and the mountains would shine. The leaves on the trees were silver, when they caught the light, every morning it looked like a forest on fire. When the autumn came, a brilliant glow though the branches...

Valerie: (referring to the Doctor) He's crazy!
Brannigan: And a bit magnificent.

The Face of Boe: He has arrived...

The Doctor: If it's any consolation, Valerie, I'm having kittens!

The Doctor: Don't go dying on me, you big old face!

Brannigan: (to the Doctor) You're very well dressed for a hitch-hiker!

"You are not alone" was first referenced in the 2006 Doctor Who Annual, which explained the history of the Time War. Shortly after the war's conclusion, The Ninth Doctor put up a memorial to honour the Time Lords, but as he departed, someone carved, in bloody lettering, the words "You are not alone". These words would later be reiterated by The Face of Boe.

This Time War history was written for the Annual by Russell T Davies.

New New York

New New York is also the name of a 31st Century city in the animated science fiction series Futurama. It is the main setting of the series. Unlike the New New York of this episode, however, that version is built on the ruins of the present day New York. Continuing the reference, it is possible that Thomas Kincade Brannigan is named after the Futurama character Captain Zapp Brannigan.