Planet of the Dead (TV story)

Planet of the Dead is the title of the first of the 2009 specials, which first aired on 11 April 2009. It starred David Tennant and featured two new characters, Christina and Malcolm, along with UNIT. Production of the special began on 19th January 2009.

It was broadcast on Easter Saturday at 6.45PM. The BBC did not officially announce the broadcast date for the special until the beginning of April 2009.

Synopsis
The Doctor, along with the lady Christina de Souza and other passengers, finds himself transported to a barren desert planet on a double-decker bus. As the Doctor and Christina struggle to uncover the mysteries beneath the sand, the Swarm draws closer.

Plot
Guards are protecting a golden cup inside a museum, later to be identified as the Cup of Athelstan, worth 18 million pounds. Lady Christina de Souza then lowers herself from the roof, and replaces the cup with a mechanical Japanese lucky cat); when the guards finally turn around at the sound of her releasing her winch on the roof, it waves at them in a mocking fashion. As the alarms go off, she runs out to the street to see someone being arrested, and she says, "Sorry, lover" to her presumed accomplice.

She then takes a back route onto the main road, where she frantically looks for a way out as police move in around her, although unaware of her presence. She runs onto a 200 bus to Victoria, where she exchanges her diamond earrings for a bus ride. Soon afterwards, a man wearing trainers, whose face we aren't shown, comes onto the bus, and seems to use psychic paper on the Oyster Card scanner. He then sits down opposite Lady Christina, and is shown to be The Doctor. After enjoying a chocolate Easter egg and engaging in some small talk with Christina, he receives an alert from the rhondium sensor in his pocket that the particles he's been looking for have been detected.

The police are still after Christina, since they know she has stolen the Cup of Athelstan, but whilst chasing the bus through a tunnel, the police witness it disappear in front of their eyes; startled, they set a perimeter around the area. Meanwhile, the bus passes through a warp into a world covered in desert: planet San Helios, apparently completely deserted. The bus is wrecked in the process. By the time it arrives at the planet the driver proclaims it unmovable.

The Doctor tells the passengers that the bus has passed through a wormhole into a different world, proving this to them by throwing a handful of sand into the space behind the bus. The sand causes a rippling effect in the air. The Doctor says that the other end of the wormhole was in the tunnel on Earth. Among the passengers is Carmen, who has been hearing mysterious voices since Christina got on. The bus driver announces his desire to return to Earth, and promptly run through the wormhole accompanied by The Doctor's "No, wait!". The other passengers of the bus witness the driver's skin and tissues melting, before he disappears into the wormhole with the same rippling effect as the sand.

Meanwhile on Earth, where the police are watching the wormhole, the driver's blackened skeleton steps out, halts, and then tumbles to the ground. Unnerved, the police declare an emergency code one, calling UNIT to the scene. Captain Erisa Magambo commands the operation and she tells her soldiers to fire at anything that comes through the wormhole.

Meanwhile, The Doctor explains to the passengers of the bus that the metal of the bus had protected them from the same fate as the driver (like a Faraday cage, as Christina states). The Doctor then attempts to call someone on Earth and gets in touch with UNIT at the tunnel. Speaking to Captain Magambo, the Doctor informs her of the crisis and speaks to UNIT's scientific advisor, Malcolm Taylor. They all set to digging the bus wheels out from the sand to try and enable them to move it back into the wormhole. The Doctor and Christina set off to explore the area, and find that there is what looks like a massive sandstorm sweeping across the planet. They are then found and captured by a fly-like alien (later known to be a Tritovore).

The Doctor and Cristina are escorted to the Tritovore's crashed ship, where the Tritovore blame the Doctor for their crashed ship. The Doctor soon explains to the two Tritovores that they mean them no harm, and are trapped on the planet just as they are. The Tritovores in turn tell them their ship has crashed on the surface of the planet where they wanted to trade with the people of the world. The Doctor, though, claims that the entire planet became a desert last year, with all 100 billion inhabitants. The Doctor then asks them to send a probe out to invesigate a 'storm' (later revealed to be a swarm of what UNIT calls alien stingrays). It send back results, showing that the storm is a swarm of billions of carnivorous stingray-like aliens, before the transmission is cut off by the probe being eaten by one of the alien stingrays. The Doctor then analyzes the alien physique by the data they get and theorizes that they must be creating the wormhole effect, by their velocity and physiology buildup, and are immune to the effects of the Wormhole because their exoskeletons are metal.

The Tritovores and the Doctor plan to get away from the planet before the swarm hits their general area, and need to get the crystal power source that makes the Tritovorian ship fly. The Doctor and the two aliens try to bring up the source manually, but the entire system is nonresponsive, lacking power. Christina, in the meantime, prepares her cat burgling equipment, and lines down the shaft. The Doctor stops her just in time before she gets diced in a security grid. After disabling it, she makes her way slowly down the shaft. The doctor tells her about himself, and some of the places he's been, including the Court of Athelstan, but he didn't remember her being there, pulling the Cup of Athelstan out of her bag.

He realises that she's a thief, and she says she prefers to say she liberates things. While getting the crystal and the brackets she sees a stingray waking behind some metal poles, and the Doctor tells her that her body heat is defrosting it, and allowing it to wake. He brings her back up. She replies she has that effect on men. Many had flown into the ship's mainframe, and that is what crashed it, he says, like birds into a jet engine. The alien stingray which was down in the shaft next to Christina gives chase, getting fried in the security grid as she turns it back on on the way up. As they run away with the Tritovores out of the ship another stingray jumps down from above and grabs one of the Tritovores, the other, in rage, prepares to fire its weapon at the Stingray but it fails, and dies as well.

The Doctor and Christina run to the bus, and after throwing away the crystal, the Doctor attaches 4 Tritovorian gravity grips onto the wheels, and uses the 5th to interface the bus steering wheel with the Tritovorian technology. However, it doesn't work. He needs something soft and malleable, suggesting gold. Christina says "I hate you", and "be careful with it". After she hands him the Cup of Athelstan, she gives him a hammer upon request, and he smashes it to bits so it fits between the bus wheel and the anti-gravity clamp controller. The bus then lifts out of the sand and into the air, flying back through the wormhole to Earth. Christina then passionately kisses the Doctor.

As the bus flies across London, several stingrays chase them through the wormhole. UNIT soldiers spot the stingrays and shoot them down. The bus lands back on the spot where it vanished. The Doctor meets Malcolm, who, in a frenzy of excitement, says "I love you!" 4 times to the Doctor. Magambo then reveals to the Doctor that they found the TARDIS at Buckingham Palace. Christina, meanwhile, is being searched by UNIT soldiers but she breaks off and runs to the Doctor. She wants to come with him for adventure and excitement, telling him that is why she steals, but he says no. When she asks him why, he tells her that he lost all his companions, and that he does not want that happening again. The police promptly arrest Christina, and take her away, leaving the unperturbed Doctor by himself.

The Doctor, about to enter the TARDIS, is told by Carmen to take care of himself; the Doctor, full of joy, tells her the same. However, she tells him "Your song is ending, it is returning through the dark, and ... over there he will knock four times." This prophecy unnerves the Doctor, possibly reminding him of his adventure on Midnight (TV story), possibly foreshadowing The Master's drum beat. (see The Sound of Drums )

Meanwhile, the Doctor decides to take pity on Christina, who is now handcuffed and being put in a police car. The Doctor points his sonic screwdriver at her handcuffs, and frees her hands. Christina gets in the police car on one side- and gets out on the other. She heads for the bus. The police chase after her, but the Doctor steps up to them and tells them to step away. The inspector charges him with aiding and abetting; the Doctor heads over to the TARDIS, saying he will 'arrest himself'. Christina then further defies the inspector, flying the bus over his head and to the TARDIS, opening the door as the others watch. Smiling down at the Doctor, Chrstina happily tells him, "We could have been so good together", revealing no hard feelings over her rejection. The Doctor merely smiles back and replies, "Christina, we were." Christina flies off into the night, the other passengers cheering her off, the Doctor merely watching; the Doctor then heads into the TARDIS.

Cast

 * The Doctor - David Tennant
 * Lady Christina de Souza - Michelle Ryan
 * Professor Malcolm Taylor - Lee Evans
 * Captain Erisa Magambo - Noma Dumezweni
 * D.I Macmillan - Adam James
 * Lou - Reginald Tsiboe
 * Carmen - Ellen Thomas
 * Angela - Victoria Alcock
 * Barclay - Daniel Kaluuya
 * Nathan - David Ames
 * Bus Driver - Keith Perry
 * Sgt Dennison - Glenn Doherty
 * Sgt Ian Jenner - James Layton
 * Sorvin - Paul Kasey
 * Praygat - Ruari Mears

Production crew

 * 1st Assistant Director - John Bennett
 * 2nd Assistant Director James DeHaviland
 * 3rd Assistant Director Sarah Davies
 * Location Manager Gareth Skelding
 * Unit Manager Geraint Williams
 * Production Co-ordinator Jess van Niekerk
 * Production Secretary Kevin Myers
 * Production Runner Siân Warrilow
 * Drivers Malcolm Kearney, Wayne Humphreys
 * Floor Runners Nicola Brown, Alison Jones, Tom Evans
 * Contracts Assistants Kath Blackman, Lisa Hayward
 * Continuity Llinos Wyn Jones
 * Script Editor Lindsey Alford
 * Camera Operators Joe Russell, James Leigh
 * Focus Pullers Steve Rees, Jamie Southcott
 * Grip John Robinson
 * Camera Assistants Jon Vidgen, Tom Hartley
 * Boom Operators Jeff Welch, Bryn Thomas
 * Gaffer Mark Hutchings
 * Best Boy Peter Chester
 * Electricians Steve Slocombe, Clive Johnson, Ben Griffiths, Jonathon Cox
 * Stunt Co-ordinator Lee Sheward
 * Stunt Performers Kim McGarrity, Jamie Edgell
 * Wires Bob Schofield
 * Choreographer Ailsa Berk
 * Chief Supervising Art Director Stephen Nicholas
 * Associate Designer James North
 * Art Department Coordinator Amy Pope
 * Production Buyer Ben Morris
 * Set Decorator Julian Luxton
 * Props Buyer Adrian Anscombe
 * Standby Art Director Nick Murray
 * Design Assistant Al Roberts
 * Storyboard Artist Richard Shaun Williams
 * Standby Props Phill Shellard, Jackson Pope
 * Standby Carpenter Will Pope
 * Standby Rigger Keith Freeman
 * Property Master Paul Aitken
 * Chargehand Props Matt Wild
 * Dressing Props Martin Broadbent, Rhys Jones
 * Senior Props Maker Penny Howarth
 * Props Maker Nick Robatto
 * Practical Electrician Albert James
 * Construction Manager Matthew Hywel-Davies
 * Construction Workshop Manager Mark Hill
 * Construction Chargehand Scott Fisher
 * Scenic Artist John Pinkerton
 * Graphics BBC Wales Graphics
 * Costume Supervisor Lindsay Bonaccorsi
 * Assistant Costume Designer Rose Goodhart
 * Costume Assistants Barbara Harrington, Louise Martin
 * Make-Up Artists Pam Mullins, Steve Smith, Morag Smith
 * Casting Associates Andy Brierley, Alice Purser

Astronomical Objects

 * The bus is transported to the Scorpion Nebula on the other side of the universe.
 * San Helios became a desert over the course of a year or under. The sand is all that remains of the dead.
 * Barclay and Nathan mention the Stolen Planets.

The Doctor

 * Carmen makes a prediction for the Doctor's future using her psychic gift: "Your song is ending, sir. It is returning. It is returning through the dark. And then, Doctor, he will knock four times." This prophecy reflects the Ood's message to the Doctor, "Your song will end soon" (DW: Planet of the Ood), as well as the warnings of darkness heard in Series 4 (Turn Left, et al); the reference to knocking reflects a similar event that occurred in DW: Midnight and the drums the Master hears in DW: Utopia and DW: The Sound of Drums
 * The Doctor's TARDIS is discovered in the gardens of Buckingham Palace, and according to the Doctor, the Queen "doesn't mind". The Queen was last seen cheering the Doctor after he saved the world in Voyage of the Damned.
 * The Doctor said that he will "never" take another companion on board the TARDIS because he has lost all his previous ones.
 * The Doctor's psychic paper is compatible with the Oyster Card scheme used for public transport in London and he uses his psychic paper to 'pay' his bus fare.
 * A reference was made to Donna Noble as the Doctor said he had a friend who called him "Spaceman" (DW: Journey's End, et al).
 * Malcolm says he had read all the Doctor's files and the Doctor asked "Really? What was your favorite? The Giant Robot?" This is a reference to the Fourth Doctor-era story Robot.
 * The Doctor's Sonic screwdriver can be used to tint his glasses to look like sunglasses.
 * The Doctor admits that he stole his TARDIS from his own people.
 * The Doctor says Christina looks like a Time Lord. He may be just getting the point across that humans and Time Lords look the same.

Foods and Beverages

 * The Doctor offers Christina the rest of his chocolate Easter egg because he's determined to keep his teeth.

Physics

 * The Doctor's device is attempting to detect Rhondium particles.
 * A wavelength parcel of ten kilohertz operating in four dimensions equals one Malcolm.
 * 100 Malcoms = 1 Bernard

UNIT

 * UNIT is called in by the police to assist in locating the bus.
 * UNIT has an automated phone system.
 * UNIT troops are equipped with H&K G36 assault rifles, M4 carbines, and Walther P99 pistols.
 * Malcolm's apparel as he leaves his laboratory is similar to that of the Doctor's fourth incarnation.
 * The Captain expresses her surprise that "Guns work".
 * This could be a call back to the Brigadier who once proclaimed he hated how so many aliens were immune to bullets.

Others

 * Malcolm named his unit of measurement the Bernard after Professor Bernard Quatermass. The British Rocket Group, to which Quatermass belonged, was previously referenced (as was Quatermass himself, vaguely) in DW: Remembrance of the Daleks. Coincidentally, David Tennant co-starred in a recent remake of The Quatermass Experiment.
 * After returning to Earth and calling Malcolm to tell him to close the portal, The Doctor looks at the phone and asks "Is that Numberwang?" in reference to That Mitchell and Webb Look.

Story notes

 * The title of the episode was unveiled during the closing credits of The Next Doctor broadcast on 25th December 2008, several weeks before production of the episode was due to begin. The title of the next special, The Waters of Mars, was in turn officially revealed in a trailer included at the end of the closing credits of Planet of the Dead, although Davies had revealed the title in an interview broadcast a few days earlier.
 * This is the first Doctor Who episode in which series producer Russell T Davies shares co-writing credit, and the first episode since the show's return in 2005 to credit two writers. The last televised story to credit two writers was the 1993 mini-episode Dimensions in Time.
 * The casting of Michelle Ryan has been reported both by media and via on-set confirmation. Ryan, best known for her work on the UK soap opera EastEnders and the US science fiction series Bionic Woman, had previously co-starred in the Steven Moffat-written mini-series Jekyll and was also reportedly a candidate for new companion after the departure of Billie Piper in 2006.
 * After initial rumours, it was confirmed that part of the episode will be filmed in Dubai, United Arab Emirates through BBC News coverage that a bus that was to be used for filming there was heavily damaged upon arrival there.
 * According to the BBC report, the damage to the bus -- a twin to one being used for filming in Cardiff -- prompted a rewrite of part of the script, the recently released trailer for the episode depicts damage to the bus identical to the damage seen in many on-set photos, suggesting that the bus getting damaged has become part of the story.
 * On 16 January 2009 The Guardian newspaper published an online column condemning the then-rumoured plan to film in Dubai, citing the UAE's human rights record. Similar criticism was posted by the fan site Kasterborous on 28 January.
 * As seen in David Tennant's video diary for this episode's read-through, Tennant feared that, having spent six months portraying Hamlet for the RSC, that he would be unable to accurately replicate the voice he uses when portraying The Doctor. In an informal discussion with Julie Gardner, he describes his voice for Hamlet as being the same as the Doctor's (being an English accent) except "more posh" and mentioned he may have to watch his previous performances as the Doctor and practice the voice. This strongly echoes Billie Piper's dilemma when she returned to film Turn Left; in interviews with Doctor Who Confidential, Piper confessed to having forgotten how to speak in Rose's accent; it was later noted that she spoke with a noticeable lisp in several scenes of that episode.
 * It has been confirmed by the BBC that Planet of the Dead will be the first Doctor Who story to be produced in high-definition; this changeover can be likened to the move from black and white to colour production in 1970.
 * According to Tennant's video diary, he and co-star Adam James have been friends for 10 years, having also worked together in the past, James is also Jon Pertwee's godson.
 * In an interview for BBC Breakfast on 7th April 2009, Russell T. Davies revealed that the episode had only been completed at 11:30pm the previous night, only 5 days before the episode airs.
 * DWM Issue 407 confirmed that Planet of the Dead was Doctor Who's 200th story.
 * Lady Christina is the latest companion to kiss the Doctor.
 * In pre-broadcast publicity interviews, Michelle Ryan described her character as a one-off companion, though like most other one-offs, such as (initially) Donna Noble, and Jenny the door has been left open for a future return.
 * The advertisement on the side of the bus reads "Unbeatable global call tariffs". On the other side it says "Tomorrow is here" and both sides say "Neon by Naismith" with the company being Neon. It is possible that this a reference to the two final episodes of the 2009 Specials as actor David Harewood has stated that he will play a character called Joshua Naismith in David Tennant's final story.
 * Lady Christina de Souza is similar to a character called 'Kate Tollinger' who was to have been introduced in a story called Crime of the Century had Doctor Who been produced beyond Survival in 1989. Tollinger would have been a safe-cracking, lock-picking thief.

Ratings

 * Easter Saturday 11th April 2009 ~ 6:45pm ~ BBC One ~ 8.41 million (unofficial overnight)

Myths and Rumours

 * Carmen mentioned in "It is returning, he will knock four times" could be Davros, or The Master.  Or it could mean something else entirely. The "knock four times" could refer to the Master, as the drumming motif that he continuously hears in his head, and that he used in The Sound of Drums/Last of the Time Lords to hypnotize the Earth's population, was a four-beat rhythm. Alternately, the "darkness" was used throughout the fourth series to refer to the return of Davros. His "song" may also be a reference to River Song, a future companion who appeared and died in Forest of the Dead; it may also be connected to the prediction of the Ood in DW: Planet of the Ood. The four knocks is also somewhat reminiscent of the Midnight Entity, a side note on that, the music from the episode Midnight was in the background as the Doctor was warned. Also when Carmen mentioned the "darkness" Davros's theme from the Season 4 finale.  Another possibility is that he is referring to the Eleventh Doctor "knocking" on the Doctor's door in a metaphorical sense, as in its the Eleventh Doctor's time now.
 * Since eccentric time lady Iris Wildthyme had a TARDIS that resembled a London bus, there were rumours she'd appear in the special.
 * Related to the Wildthyme rumor, speculation regarding the identity and true nature of Lady Christina, following statements by Davies that she would have a profound impact on the Doctor, included the possibility that she might be a Time Lord, and perhaps even a known Time Lord such as The Rani or Romana. This ultimately proved not to be the case, although the Doctor's comment to Christina, "You look Time Lord" (filmed in January-February 2009, after the speculation began) might be a reference to the rumor.
 * Michelle Ryan is one of many young actresses rumored to be contention to appear as companion to Matt Smith's Doctor. In pre-broadcast publicity, Ryan stated she considered Christina to be a one-time companion. As of April 2009, however, casting for Smith's co-star has not yet been finalized.
 * The Radio station, Neon, advertised on the buses in London is part of the story arc for forthcoming episodes.

Filming Locations

 * Cardiff, St Mary Street - the first scenes with the red bus driving down the road with the Doctor and Christina stepping on to it
 * Cardiff Bay - Police and UNIT investigating the disappearance of the bus through the wormhole
 * Dubai, United Arab Emirates

Discontinuity, Plot Holes, Errors

 * Do the International Gallery guards really not look at the item they're guarding? It is implied they aren't very good at their jobs, for comedic purposes. The guards might have thought that the item they were guarding wouldn't have been stolen as soon as they started the job. They were probably just getting settled in.


 * Would the security lasers around the relic in the museum not have a roof of some kind? Haven't they worked out that thieves can enter the museum from above? The museum might have thought that the guards would look out for that sort of thing. Referring to the point above, they obviously didn't.


 * When the bus is originally shown, it has a number plate of W974GHM, but later, when flying, its number plate has changed to RUA467W. This could be, if the rumor is to be believed, that the Doctor Who team had a bus stolen while they were filming in Dubai and had to replace it This is most likely because, as seen in the confidential, the team used two separate buses (one for shots in Dubai, one for shots in the UK). However, in-Universe, this point stands, and is still a continuity error.
 * The Doctor claims that it will take the Swarm 20 minutes to reach them 100 miles away. So therefore they were moving at 300mph. However, when Christina was being chased by one it could not catch up despite her moving at a much slower speed. This one had been inactive for an unknown amount of time, due to the low temperature of the ship, so it's reasonable to assume this is why it was so sluggish, as most beings become slow if they are exposed to cold for a certain amount of time. It was also mentioned in the script that the swarm had been gaining speed constantly while circling the planet.


 * Why did the Tritovores have ear pieces? They clearly don't have ears. The "ear pieces" were referred to as a means to communicate, not that they were meant to fit over the ears. They could just as easily have been fitted to be over the Tritovore's mouths, meaning that the fact that they fitted on human ears could have been a coincidence


 * The rays were travelling in a swarm; how did only three manage to get through when they were all going through together? They could have simply been farther ahead of the other rays, or scouts of the "new world. They were travelling round and round the planet. Or they could have been the rays from the Tritovore ship.


 * The bus is seen to take on damage as it travels through the worm hole, but on its way back to Earth, no more damage to the bus is sustained.  The bus took damage because the wormhole was too small when it first travelled though, but by the time of the second trip the wormhole was much larger.


 * Surely companions like Jack Harkness or Martha Jones aren't exactly "lost"? The Doctor was mainly referring to recently-lost Donna, as well as Rose, Adric, Katrina and others who he has lost over the years. And he means they literally don't want to travel with him anymore, because of Torchwood and UNIT. So to him, they are lost.


 * Why did Carmen not see that they were going to survive? Carmen may not be able to see everything, just certain things. Her visions are vague.


 * There are tire tracks behind the bus, proving it drove to its location. The tire tracks could be evidence that the bus was forces forwards when it came out of the worm-hole, which made impressions in the sand. It was shown on Doctor Who Confidential that the Doctor Who Team went to great lengths to ensure the sand was flat and undisturbed meaning they would have removed them behind the bus should they not have been needed.


 * When Christina escaped the police car at the end, why didn't all the hundreds of heavily armed UNIT troops not try to stop her when she just ran past them? UNIT isn't the police - quite simply, it's not their job. And considering how dismissive Capt. Magambo is of the police, they may not even know she's wanted. They could have also been a bit preoccupied with clearing up the remains of the stingrays.


 * After seeing its fellow eaten why didn't the other Tritovore just shoot the stingray with its weapon. It might have been panicked and done attacked the Alien Stingray instead of running. It looked like it tried to, but was too scared and got eaten before it could.


 * The cannon the UNIT troops are using is seen being fired several times out of four nozzles but only one of the rockets seems to hit the Stingrays each time. Obviously the camera wouldn't follow each shot as they left the barrels, and the same reason applies for when they hit the stingrays; the other shots simply missed


 * Police cars can't be opened at the back from the inside, so how did Christina escape? She is a master thief, she probably knows how to open a secured door.


 * Why didn't the Doctor just ask UNIT to send an all terrain vehicle or helicopter through the wormhole to pick up the survivors? Or other supplies for that matter? He probably didn't want to make things worse, or incite UNIT to send troops into an unknown situation.


 * After she steals the cup Lady Christina goes back through the roof. So why is she back in the museum the next time we see her? Christina obviously climbed down into the building. This is likely because the guards were expecting Christina to leave the building behind quickly, not that she would stay right under their noses. Alternatively, Christina could simply have climbed through the ducts, and was travelling through the museum halls as a quicker way of getting to a necessary duct; she probably wasn't expecting her calling card to be noticed so quickly

Continuity

 * As this episode is the 200th storyline of Doctor Who, the episode makes an in-universe reference to this by calling the bus The 200.
 * Several bus passengers discuss the events surrounding the relocation of Earth to the Medusa Cascade (per DW: The Stolen Earth/Journey's End), which places this story as taking place after those events, while confirming that, unlike the Battle of Canary Wharf, there seems to have been no attempt to "cover up" what happened, and it remains public knowledge.
 * The Doctor mentions "Humans on a bus, always blaming me", referring to the bus accident in DW: Midnight.
 * The Doctor mentions the K1 Robot that featured in DW: Robot, when asking Malcolm what his favourite file about him was.
 * UNIT at last meets an alien race that's not immune to bullets DW: Robot or as Captain Magambo puts it "I don't believe it, guns that work", this also refrences the events of The Sontaran Stratagem where UNIT's weapons are rendered useless.
 * Carmen says "Your song must end soon" which is what the Ood also said to the Doctor in DW: Planet of the Ood.

DVD and Other releases
According to Amazon.co.uk, a Region 2 (UK) DVD release is scheduled for 11 May 2009, although as of the end of March no official announcement has been made by BBC Video or 2 Entertain. A release one month after broadcast is in keeping with the precedent set by the release of The Next Doctor to DVD. It is not yet known if the release will have any extra features.

As with The Next Doctor no North American DVD release has been hinted at; it is assumed it will at least be included in a box set collecting the 2009 Specials and The Next Doctor; such a release will not occur until the first quarter of 2010, at the earliest, pending broadcast of the remaining specials in the UK.