Frau Clovis' name is misspelled "Fran" in the end credits.
The Doctor notes the only thing missing from the hospital is a shop. This is alluded to in the third season premiere when the Doctor notices the hospital he is in actually has a shop.
The TARDIS is in a different location at the beginning of this episode compared to the final scene in The Christmas Invasion, implying there may well have been other adventures between these two stories (i.e. Attack of the Graske) but some references to the Doctor being a new Doctor do imply that only a little time has passed since Christmas.
The ailment that the Duke of Manhattan is dying from, Petrifold Regression — a disease that turns its victims to stone — is also mentioned in the Tenth Doctor Adventures novel The Stone Rose by Jacqueline Rayner.
The bit where Rose (possessed by Cassandra) kisses the Doctor wasn't originally scripted.
David Tennant's first scene with his costume, consisting of a coat made of upholstery material, was at Cassandra's party.
Cassandra says that being inside a male body is an entirely new experience. But in The End of the World, she said she was born a boy.
This is the first episode of the new series that does not take place on, or in orbit above, the original Earth.
At the beginning of the episode where Rose is hugging Mickey and Jackie you can see the outline of BAD WOLF written on the ground in chalk from the end of last season.
The Face of Boe says that being millions of years old is impossible. However, this conflicts with his appearance in Episode 1-7, The Long Game, which was set in the year 200,000. If it is the same Face of Boe, he wouldn't just be millions of years old, he would be billions of years old, as this episode is set in the year 5 billion and 23.
(When the Face of Boe says this, he seems to do so with a knowing wink. In other words, it's impossible because everyone KNOWS it's impossible, but he and the Doctor might know better.)
Also, the Face of Boe does not have to be one being. It may just be a position, as in the head of the solar system Boe
This episode is the first time that the Face of Boe is heard. In his other appearances in Series 1 (The End Of The World, The Long Game), he was only seen, and never spoke.
Cassandra-Possessed Rose: You're not exactly nun with gun, you're not even armed.
Matron Casp: Who needs arms when we have claws?
The Doctor: Nice place. No shop, downstairs. I'd have a shop. Not a big one - just a shop. So people can shop.
The Doctor: Strictly speaking it's the fifteenth New York since the original. So that makes it New, New New New, New New New New New New, New New New, New, New York. (Rose is staring at him) What?
Rose: You're so different.
The Doctor: New New Doctor.
Cassandra-Possessed Chip: Oh sweet lord, I'm a walking doodle...
The Doctor: If they live because of this, then life is worthless.
Novice Hame: But who are you to decide that?
The Doctor: I'm The Doctor. And if you don't like it, if you want to take it to a higher authority: there isn't one. It stops with me.
(After Cassandra possesses one of the Flesh so that the Doctor and Rose can escape, she jumps back into Rose's body)
Cassandra-Possessed Rose: Inside her head… they're so alone. They keep reaching out just to hold us. All their lives… and they've never been touched.
Matron Casp: Anything we can do to help?
Cassandra-Possessed Rose: Straight to the point, Whiskers. I want money.
Matron Casp: The Sisterhood is a charity. We don't give money. We only accept.
Cassandra-Possessed Rose: The humans across the water pay you a fortune. And that's exactly what I need. A one-off payment, that's all I want. And perhaps a yacht. In return for which, I will tell the city nothing of your institutional murder. Is that a deal?
Cassandra-Possessed Rose: The Sisterhood are up to something. Remember that Old Earth saying? Never trust a nun. Never trust a nurse. And never trust a cat.
(About the Duke of Manhattan's miraculous recovery)
Matron Casp: Primitive species would accuse us of magic. But it's merely the tender application of science.
The Doctor: How on Earth did you cure him?
Matron Casp: How on New Earth, you might say.
Novice Hame: (about the Face of Boe) I can hear him singing sometimes. In my mind. Such ancient songs.
The Doctor: Am I the only visitor?
Novice Hame: The rest of Boe-kind became extinct long ago. He's the only one left. Legend says that the Face of Boe has watched the universe grow old. There's all sorts of superstitions around him. One story says that - just before his death - the Face of Boe will impart his great secret. He will speak those words only to one like himself.
(Rose and Cassandra discuss Cassandra's regeneration)
Rose: What about the skin? I saw it. You got ripped apart.
Cassandra: That piece of skin was taken from the front of my body. This piece is the back.
Rose: Right, so you're talking out of your ar...
Cassandra: ...ask not.
Cassandra: Rose Tyler! I knew it! That dirty blonde assassin!
Chip: She's coming here, mistress.
Cassandra: This is beyond coincidence. This is destiny. At last I can be revenged on that little-
(Cut to the Doctor and Rose entering the hospital)
Rose: Bit rich coming from you.
The Doctor: I can't help it, I don't like hospitals. They give me the creeps.
Cassandra-Possessed Rose: Oh my god! I'm a chav!
The Doctor: Hold on, I can understand the bodies, I can understand your vows. One thing I can't understand, what have you done to Rose?
Novice Hame: I don't know what you mean.
The Doctor: And I'm being very, very calm. You wanna be aware of that, very very calm. And the only reason I'm being so very, very calm is that the brain is a delicate thing. Whatever you've done to Rose's head, I want it reversed.
Novice Hame: It's said he'll talk to a wanderer, to the man without a home.
(The Doctor realises that he fits this description.)
Novice Hame: The lonely god.
(After being kissed by Cassandra-Possessed Rose)
The Doctor: (high-pitched voice) Yup...still got it...
Cassandra-possessed Doctor: Goodness me, I'm a man... Yum!... So many parts! And hardly used... Ah.. ah! Two hearts! Oh, baby, I'm beating out a samba!
Rose: Get out of him.
Cassandra-possessed Doctor: Ooh, he's slim. And a little bit foxy. You've thought so too. I've been inside your head...You've been looking... you like it!
Cassandra Possessed Doctor: (pushing Rose aside) Out of the way, blondie!
The Doctor: That is enigmatic. That - that is - that is textbook enigmatic.
Rose: (Talking about Chip, to Cassandra) What about Gollum?
Rose: They are cats!
Rose: So where we going?
The Doctor: Further than we've ever gone before!
Cassandra Possessed Rose: Oh...baby...It's like living inside a bouncy castle!
Rose: Can I just say, travelling with you, I love it.
The Doctor: Me too!
Cassandra-Possessed Rose: Over the years, I thought of a thousand ways to kill you, Doctor. And now that's exactly what I've got. One thousand diseases.
The Doctor: When you took your vows, did you agree to this?
Novice Hame: The Sisterhood had sworn to help.
The Doctor: What? By killing?
Novice Hame: They're not real people. They're specially grown. They have no proper existence.
The Doctor: What's the turnover, hmmm? Thousand a day? Thousand the next? Thousand the next? How many thousand? For how many years? How many?!?
Rose: Don't you come anywhere near me, Cassandra.
Cassandra-Possessed Rose: Although...Nice rear..bumper!
The Face of Boe: We shall meet again Doctor, for the third time, and the last time, and the truth shall be told. Until that day...
The Doctor: (Pointing to Cassandra-Possessed Rose) You can't deny them, 'cause you helped create them!
Rose: What's the city called?
The Doctor: New New York.
The intensive care unit location was the same place used for the warehouse in the episode Rose, which is an abandoned mill in Cardiff.
It took three hours to make up a cat nurse using a veil and mask.
Turkey: July 11, 2010 on CNBC-e
The outside curved tower of the hospital looks a lot like the Burj Al Arab hotel located in Dubai, United Arab Emirates.
A working title for this episode was Body Swap.
Novice Hame and the Face of Boe return in series three's Gridlock.
The final viewing figure for the BBC One airing of this episode was 8.62 million.
For her scenes playing the Cassandra-possessed Rose, Billie Piper wore a Wonderbra and a slightly different shade of lipstick. She also unbuttoned the top buttons of her shirt.
The scene where the Doctor, Rose and Chip leave the TARDIS and arrive at Cassandra's party, was the first scene David Tennant shot in his new costume. He spent most of The Christmas Invasion in an Arthur Dent-type dressing gown.
The Gower Peninsula in Swansea was used for the first scene, when Rose and the Doctor appear on New Earth; also, the entrance hall of the Wales Millennium Centre in Cardiff doubles as the entrance hall of the hospital.
Russell T Davies got the idea for this story from the material he wrote for the book Monsters and Villains in 2005. He was writing a biography of The Face of Boe's life and came up with the secret that he will tell...
Cassandra has set up in her lair an old-fashioned movie projector, and is watching a movie of herself when she was younger and more beautiful (and had an actual body). This may be an allusion to the movie "Sunset Boulevard" (1950, dir. Billy Wilder), in which one-time silent film star Norma Desmond (Gloria Swanson) uses a movie projector to show the films in which she appeared and exults over her own beauty and talent.
Cassandra-Possessed Rose: Oh my God, I'm a chav!
Chav is a mainly derogatory slang term in the United Kingdom for a subcultural stereotype fixated on fashions. The defining features of the stereotype include clothing in the Burberry pattern and from a variety of other casual and sportswear brands. Tracksuits, hoodies, sweatpants, baseball caps and cheap bulky jewellery are particularly associated with this stereotype.
Rose: What about Gollum?
Gollum is the character from the Lord of the Rings trilogy obsessed with the one ring, which he called "My precious."